How long does it take for a cockatiel's flight feathers to grow back?

I purchased a baby (10 week old) cockatiel a week ago. The breeder routinely clips flight feathers on their young birds. I'm guessing this is to aid in hand taming, since my bird is extremely tame and friendly. Both the breeder and my avian vet recommend that birds be allowed to become fully flighted as they mature, and I would love for my cockatiel to be able to exercise by flying around inside my house.

How long does it generally take for a young cockatiel to regrow its flight feathers? My little guy keeps trying to fly, and it's sad to watch him "thump" to the ground.