At NYCOM, you can do 3 electives in your field of choice. I will be doing all 3 of my electives in PM&R. Each one in a different state since I am leaning, very heavily, on doing residency outside of NY. NY, especially Long Island, has become too expensive to live in.
In general, 2 electives in good enough for most people since most students, especially DOs, eventually want to go into a primary care specialty (IM, peds, FP). However, with specialties like PM&R and anesthiology, you do not get any true exposure until 4th year. IThis is why doing 3 electives in the same field is important for someone like me. 4 electives may be excessive unless it is something ultra-competitive like derm and ortho.