If you prefer bikinis, WEAR THEM! I don't think there's an "inappropriate" age.
I haven't worn a bikini. Maybe when I was a kid but I don't remember. Since I started puberty, the swimwear shopping became a frustrating experience. I'm currently wearing a 30H bra, so imagine how hard it is to find in your average store something that covers and supports that size (and back in the day I didn't know my true bra size). I usually used to buy boring tankinis and the fit was "meh". The style was secondary, it was not "me", it was more "this is what is available and looks decent".
My back is like a S or M and my boobs are more than an XL, in swimsuit sizes. A couple years ago I bought a tankini from the maternity section (yeah, because these guys think that only pregnant women can have big boobs).
Well, this frustration was before I discovered ONLINE SHOPPING. Last year I bought a blue velvet swimsuit from Modcloth. It's gorgeous. Yes, it's "traditional" because it's an one-piece, but it has a retro vibe and it gives me a nice hourglass shape, and the support is great. I feel glamorous in it and confortable.
I recently discovered that ASOS carries bikini tops in +DD sizes. It looks like they offer good support and shape. Maybe this summer I'll jump in the wagon of the bikini!
So, see? I'm 23 and haven't worn a bikini. If I were you, I would take advantage of it! I'm sure they suit you great. Wear what makes you feel more "you"