Depends on what they're doing. I understand staying at home if you're saving for a house deposit or studying. Other than that I wouldn't only start questioning it at about 25 if they were showing no plans at all of leaving. Not because I want them out, but just because I'd want them to experience some independence and develop life skills. I don't think it's black and white, though. DEFINITELY need to be contributing either financially and/or with helping around the house considerably once they are out of school though - do own laundry, pay board, other agreed duties.