From a fetish development standpoint, it probably dried up when magical girls stopped going from 8 to 18 when they used their magical item and instead only had a costume change as 14-year-olds. In addition, straight up aging expected from a non-hentai Japanese character isn't going to end up with huge tits unless it's supposed to be a joke. (pic is Kari from Digimon in some epilogue thing)

Beyond that, there does seem to be a tendency for safe horny to care about the girl's original age before she got hit with a 13 going on 30 spell or whatever.