I believe the general rule of thumb is 6 weeks as an incubation period, but I usually only leavemine in for 3 weeks. As soon as the fish is eating well, shows no signs of any injury or disease I move them over. Usually by this time, they are coming to the front of the tank for food rather than hiding which is a good indication they are de-stressed.
Remember to take your time to acclimate them to your main tank, turn off the tank lights as you introduce the newcomer and if you have any aggressive fish, rearrange the rockwork giving the newcomer ample opportunity to seek out a new cave of its own.