Is it normal for my boyfriend to like younger women?

First let me start with how my boyfriend and I met. He first saw me when I was about 16/17 shopping in the store that he worked at in the mall. He was about 21/22 at the time. I started working at the store shortly afterwards and this is how we got to know each other. We stared dating about four years later and that is when he admitted to me he was attracted to me back then but he obviously never acted on it. Over the years I have noticed that when he has a crush on another girl they are quite a bit younger than him. One was 17 when he was 26 (obviously he never acted on it and I don't think he knew she was under 18 at first…) and more recently I found out about a crush he has on a 21 year old that I know and he is now 30. I am concerned because I worry that as he gets older he is going to continue preferring girls in their early 20s and he will become a massive creep. I am five years younger than him and he has always been proud of that. Is this normal or should I be creeped out?