How long will a phantom pregnancy in a rabbit last?

Answer 1

A false pregnancy? Breed her as soon as you can.

But, unless you are positive there's a market for your rabbits, do not breed them at all. There are rabbits in shelters all over the country, and when their time runs out they are put down even if they're healthy. It's terribly irresponsible to add to this overpopulation, or to bring new lives into the world just to "cull" them because no one wants to adopt them. Even if you know there is a market for your rabbits, consider this: all those customers of yours could be rescuing rabbits from shelters, intend of buying your rabbits that don't even exist yet. However, the final point is this: if you don't know what you're doing, don't breed your bunnies: instead, spay/neuter them. False pregnancies are stressful for rabbits, and you're doing them a favour by spaying them. See the related questions below for more details.