I took a night class in organic chemistry at 30, considering a career change that I never pursued. It was fantastically challenging, which was what I needed at the time (I wasn't getting enough from my job). After the experience, I completely understand why this class serves as a proxy for medical school admissibility. For someone who almost never studied, I suddenly found myself doing an hour or two of homework each night. Going back to school and getting the 'A' from a top 10 university was one of my proudest academic achievements. I highly recommend taking a few classes out of your comfort zone to recharge your batteries.