It depends. Lots of variability from lab to lab, seed to seed, medium to medium. Some will germinate within weeks, some will take months. Replating is the same - some will take months, some years. How many replates will you do per batch? Frequent replates can push the seedlings by always providing fresh media, but more transfers equals more chance of contamination.
Sorry so vague, but there is no easy answer in orchids.