Yes, I would definitely recommend trying to lengthen sessions, but time is both limited and relative, so here are some other personal reflections you might find useful regarding both time and bodily sensations. Obviously, all of these (somewhat rambling) reflections are provisional and based only on my own current understanding of where I am in my own meditation.
First, the more worldly garbage that builds up in the mind between sessions, the more time that must be wasted at the beginning of a session in “emptying the garbage.” So follow the precepts, engage in right speech, guard the sense doors, and avoid anger and other strong passions so as to prevent the accumulation of unwholesome worldly kamma throughout your day, the fruits of which then pollute and defile your mind during sitting, and have to be dealt with in the initial stages of the sit.
Mix in walking meditation and other briefer meditation sessions and skillful reflections during the day as much as you can. The more you can approach making all of your life bhavana, the easier it is to achieve peace and absorption quickly in sitting sessions.
I found my own sitting session lengths stretched out of their own accord. Once you get better at identifying and letting go of the hindrances, then the various urges that make you want to get up in the first place start to abate. My late nighttime sitting session had stretched out to an hour and a half - sometimes two hours. However, I have had to cut them back a little due to knee issues. I try to compensate by sitting more than once each day. I also changed my sitting posture. However, I have also found that less time these days is consumed in getting to where I “left off” so to speak in the previous sessions. I have recently had some half hour sessions that were really “deep.” On the other hand, I have had 90-minute sessions that were frustratingly cluttered with mental junk. So it goes.
The body is a nearly endless field of sensations, so there is no telling anyone which ones can be potentially skillful objects of attention. I’m sure attending to pulse sensations could be useful. ( I used to attend to the ringing in my ears, since I have tinnitus.) Personally, I have found it more important to stay with the heart itself, as well as the sensations around the heart, in the chest and solar plexus, and the way these interact with breathing. For me this is all bound up with attending to emotions/sankharas. Fear and dread, anger and other painful emotions consist in part of a range of bodily symptoms, reactions and responses - many of which are experienced in the body core. Whatever you do, keep in mind that the whole point is to release, and move in the direction of where suffering ends. The point is not to build up (and - hard work - maintain!) a mental encyclopedia or scientific compendium of bodily observations.
Interesting question to ask about bodily sensations: Is the bodily component of an emotion always a response to the mental component, or is the mental component sometimes a response to the bodily component? Is my chest tight because I’m afraid of something? Or do I think I’m afraid of something because I feel my chest tightening? Similar questions can be asked about other bodily phenomena.
Your body is your burden. Keeping your head erect and sitting on the top of your spine is hard work. Keeping the whole body erect and coordinated, with the torso and head balanced your hips as you walk is hard work and a miracle of mechanical engineering. The beating of the heart and pushing of blood through arteries and veins against atmospheric and bodily pressure is hard work. Protecting the beating heart from potential dangers is ongoing work that your body has been programmed to perform since the womb. Responding either impulsively, or with some intellectual assistance, to painful sensations as they arise is part of the burdensome bodily programming. Pay attention to the painful struggle of this burden, and search for the direction in which it is put down.
Meditation is physically relaxing, and relaxation is good and pleasant, and conducive to going further in your meditation. But it is easy to get hung up on the project of relaxing the various parts of your body itself as though that itself is the point of it all. There are some painful sensations that are just not going away as a result of relaxation. At that point, one must endeavor to attend to the feeling of these sensations as feelings, and the processes of desire/aversion, and I-making and my-making, that accompany the feelings (My neck hurts; I am a person whose neck hurts; I want a state of being that does not include my neck hurting, etc.)
See if you can attend to the larger experiential “space” in which all of those bodily sensations are taking place. Where is its boundary? Does it have a boundary? What feelings and sensations comprise that boundary? Can I “permeate” the entire sphere of my conscious awareness with a cool, peaceful kindness that does not differentiate inner and outer sides of the boundary?
Question: How does my aversion to painful sensations contribute to the creation of a strong sense of self? (Under “painful sensation”, I also include desire - which is the painful consciousness of the non-presence of some imagined pleasurable state.)
The whole point of the path is the understanding of, and release from,dukkha. When I’m stuck, I sometimes say to myself, “Find the dukkha.” The more kinds of dukkha you see, the better you get at letting go of their causes, even before they bear full fruit, and the more concentrated you get. The more concentrated you get, the more subtle and interesting are the forms of dukkha that can be seen as they are. Besides the hindrances, I often find myself identifying and examining such experiences as:
Grief and loss
Anxious feelings of obligations or things left undone
Purposelessness or meaninglessness
Aesthetic feelings of distaste or revulsion related to things in one’s environment
Aesthetic feelings of distaste or revulsion related to one’s own body
Pride and feelings of superiority
Shame and feelings of inferiority
Fear of my own death
Fear of the death of others
Fear of future pain
Resentment of others over my attachments to them
Confronting dukkha is frightening and something to which we are strongly averse - like confronting a yakkha in a dark forest at night. But if you don’t confront sufferings and subdue them, they will always be there looking over your shoulder and tormenting you.
Avoid the urge to fully cognize, conceptualize and classify bodily sensations and mental phenomena. For example, when anger arises, its seeds blossom into anger, then the anger proliferates into other things. You might think as you observe it “Wow, I’m really angry.” But later, as you develop skill in letting go, you feel the first little seed of the anger process sprouting, and drop it quickly before it flowers in to anger. It is not necessary, or desirable, to stop and ask “What emotion was that that almost arose?”
Smile gently. Your mind responds to bodily actions by entering into states appropriate to those bodily responses.
The world is run by the armies of Mara. By seeking the place where suffering ends you are moving up and back against against the stream in which all life flows. The human social world doesn’t want you to stop suffering, since many of those sufferings are functional from the moral-teleological-social point of view. Even your evolutionary heritage as a human being is not entirely friendly to your awakening. “Nature” doesn’t want you to get enlightened. It wants you to eat, fear, run, fight, screw, reproduce and keep samsara going. It gave us some “reason” to help perform these tasks more efficiently and out-think some of our animal competitors. But evolutionary nature seems to have overlooked something and left us an escape hatch to thwart it’s imperious and ultimately futile animal drives.
Be aware, and attend to the fact, that you are afraid of your own potential nibbana. All of us unawakened people are afraid like that. The reason it is so difficult to achieve deeper levels of seclusion, concentration, absorption, etc. is because we often have a panic reaction to the experience of freedom and groundlessness. All of the deeper attainments other than nibbana itself involve re-establishing a ground, and abiding in and clinging to some deeper “base” as a standpoint from which to let go of some coarser base. Then we begin to work with that new ground and look for the path to letting go of it too, and going deeper. But the end of the process is supposed to involve the complete freedom of clinging nowhere, abiding nowhere. That’s scary, and like jumping out of a plane, is something you are at some level very resistant to doing. I think that’s why the Buddha gave so much attention to subduing fear and dread.
Speaking personally, I have found the various manuals of minimal guidance after the initial stages of meditation, and the suttas to be a much better guide. Ultimately, you have to wander alone in your own experiential forest and find paths than move toward peace and release. There is no step-by-step map or recipe book, but the suttas describe major landmarks.