I can't say that I would recomend a dildo being inserted for longer than a few hours. I've known women to have tried this and there is oftne bruising and infections. Also, if the didlo is hard and stiff it can cause rips and abrasions which can lead to infections and scar tissue build up.

On the other hand, I have had a few girls wear a plug for very long periods of time with no trouble. When I say long periods, I mean for days at a time with the exception of washing and the obvious toilet needs. Of course, the plug was of the softer variety and not terribly stiff.