Depends on the situation in my rabbitry.
If the doe lost her litter, she'll be bred the next day as long as she looks healthy, and her bits are mostly back to 'normal.'
The next criteria here is if I need a litter by a certain time. Like for my fair coming up, I have to have the does bred by a certain date. They're all due to kindle any day now... So they will be rebred when the kits are 5 or 6 weeks. Earliest would be 3/4, if need be. (I haven't done the math. I believe they'll have 5 weeks, but I can't remember for sure.)
Just like the fact that I tend to let my does wean their babies. That, or when the buck's start fighting, and theres interest in brother/sister. Usually 12 weeks is about the latest.
=D