I have two burmese around 10ft each. We feed them a large rabbit biweekly or so, but it really depends on their behavior. You definitely shouldnt feed it a rabbit a week, IMO thats too much.
Then again, im talking about large rabbits, not bunnies. Theres not an exact science behind it to me, i just base it on observations and it has worked well so far.
I love burmese, but you have to know what youre getting into. Mine are MAYBE 2 and a half to 3 years old. That time will fly by as well. The snake will easily push 15ft, and might get into the early 20's.