According to the M1/M2 Curriculum Committee Chair, we schedule NMT 24 hours of our students time per week. Of that time, NMT 8 hours, and normally 6 hours will be lecture-based. Most weeks there will be 2 hours of clinical skills lab to ensure that the clinical aspects of what you are learning are closely tied to the mainly basic sciences that you are learning. Other teaching/learning is based on the block and information but would most often include some team-based learning, labs, case-based experiences with scenarios or live patients conversing about coping with xxx situation, etc. While we have very few manadatory hours, the integrated methods of teaching/learning would cause you to miss quite a bit if you did not attend.
As for the preceptorships they are split with a bit of a different focus in years 1 and 2. The first year focus is to get you really good at patient history/physicals and presenting to the preceptor. Therefore you will likely be with a primary care doc the first year because they do this routinely, and you will be good at it after the initial year. The second year is split in half whereby you will get two additional specialty experiences with two separate preceptors, likely in two different environments. I think that you will be required to do a certain number of 4 hour preceptorships each year (I think it might be more than 8, maybe 11?? I could be wrong) and you can do more if you desire. In each case the preceptor understands what your curricular focus is at the time and gets you "reps" in practicing xx procedure, etc.
As for other commitments, the preceptorships are outside of the 24 scheduled hours. The only other thing that comes to mind that is done outside of the 24 scheduled hours is your FIRE "research" project that spans the initial two years. While there are some milestone events that you must meet along the timeline, different projects will be more/less time intense. There are many ways to work this depending upon the way you like to work. If you are a meticulous schedule person your can do 2 hours per week for two years, others may do the bulk of it during the summer between the first two years; do something that you like and be as structured or flexible with it depending upon how you prefer to work.
I hope that his clarifies.