Age is nothing but a number ...?

So I need some opinions... I'm 18 going on to 19 and I'm dating a 27 year old ... Is that bad? I don't think it's too bad. He's very mature and a gentleman. I'm so happy with him and that's all that matters right? He doesn't see me as "young" due to my maturity also. He throws out compliments and isn't afraid to show me off in public, but should I think twice about it ?