They are able to breed as young as 4 months, so it's a good idea to separate them by then. You don't want them bred until they are at least 8 months or older. If you're comfortable waiting until they are a year old, then it is actually better for them. They are more mature.
Andi in OK
First off- what breed is your bunny?
Most rabbies are best bred when they are 7-10 months old by that time most buns are mature enough. I would advise breeding rabbits before they are a year old because it can be harder to get an older rabbit to conceive... especially the large breeds like flemish giants. (And yes I speak from personal experience.)
Hope that helps.
Also so you know alot of first time does lose their first litter but not taking care of them or not having the litter in the box and spreading the babies everywhere. So I never count on a first litter from any doe. Although there are some that will do great. Just thought you should be warned. I always try to make sure at least 3 does are due at the same time that way there is a foster mom if needed. I have a couple nice holland lop does for sale( with pedigree) and some mini rexes, but I don't ship so that probably doesn't help you.