Anything past the initial 8 year contract (sounds like you may have already completed this) is not a mandated contract length if you do not take MDSSP, STRAP, or HPLRP. If you decide that you want to resign your commission in the second year of med school, you can do that as long as you didn't take out a stipend and you are past the initial 8 year contract. Had a couple dudes in my old unit that did that (one after 3rd year and the other after graduating).