winter break. I wanted it done before summer/applying. Ended up being about 4-5 weeks of studying and taking it the first weekend of the spring semester before labs and homework/studying kicked in.
The textbook answer is to take it when you're ready. I'm too methodical for that. I just picked a date and went with it. My scores don't reflect my ability, but i was convinced they would do and crossed the dat off my to-do list.