I believe on the Daily_Lolita community on Livejournal there is one or two Lolitas on there in their late 30s to early 40s. They still look great!
I'm still going to dress in Lolita even when I'm older. There's no age limit on Goth fashion either, so I suppose as long as I tone down the poof and ribbons it'll still look perfectly fine.
Heck, I'll still wear Lolita when I'm 80. Won't I be the cutest grandma ever? lol