By the time I apply this cycle, my LOR's (one from MD, one from DO, one from genetics prof, one from science writing capstone prof, and one from my epidemiology prof) would have been all roughly a year old. Is this a problem?
It sounds like you are feeling a bit anxious about this. If it would make you feel better then you can absolutely ask your LOR writers to just update the dates. However, I want to assure you that it really is a nonissue and completely unnecessary.
There may be things to stress over during the application process, but having 1 year old LORs isn't one of them. Good luck next cycle!