I never could find an exact time to wean mice either when I started, but I seem to do it when they start running around the cage (like madness, LOL) and nibbling stuff. It seems like momma nibbles food and leaves it around the tub for them, so actually seeing them eat at the food dish is rare for me. Usually when they look like they are bouncing off the walls I just pull them. LOL!! I think it ends up being about 4 weeks like rats.