varies...
I heard it once put that 100% will be say bred/hot between a 1 month period... but some farms areas will be hot for 1 week, 3 days here and another will be hot at another time.
so overall it's about the same year to year but individual areas can change/vary a good bit.
also buck/doe ratios
good luck.
personally I've seen a property be hot say tues, then wed to fri nothing then it might heat up again, I think it just depends on when individual does in your area become hot, and that'll vary.