Rotation Feeding for Kitten

At what age is it okay to be rotating canned food for kittens?

Jamie was 10 weeks old when we brought him home and already insisting on lots of variety, which wasn't easy with kitten food. There weren't too many decent brands of kitten food in those days (1999). As long as the kitten isn't reacting with diarrhea or vomiting, rotating foods shouldn't be a problem.