I don't think there's any age limit; although I would prefer not to bathe a really tiny kitten (way, under 4 weeks) just because they don't have enough "padding" to be able to fully regulate their body temperature and they could get chilled easily. Just be careful about getting water in the ears and eyes.
my cats hate water too... but when i first got tyra, she was a DIRTY LITTLE GIRL. so... we waited until tle doc said she could be bathed (after her spaying scars healed) and then we bathed her. she was about 4 months old... but she was so dirty that she made me kinda allergic.
Tierney gets a bath once a month. And Teagan really needs one.. she is stinky!!!
Tierney has never really learned to completely clesn himself, he didn't have a mom, and i wonder if that is why. Although, Tierney is bathing Teagan, and she is smelling better everyday. I am going to hold off on giving her a bath a little longer, and hopfully she wont need them like he does!