Should I be concerned by my boyfriend 'liking' provocative photos of other women on facebook?

[Andrea]

I have been going out with this guy for about 4 months. He's 42 and I'm 29. I wouldn't say we were "in love" but things have been going quite well although it's still kind of early days. Although we are quite different in some ways, I do like him, and he treats me well - pays for meals, gives gifts, flowers, cards, compliments me etc, and even recently paid for me to go for a holiday in France with him. Because of his age and things he has said, I know that he is looking for a serious relationship, not just a casual fling.
However, I am a bit bothered by the fact that he sometimes 'likes' pictures of girls on facebook... These are not his friends - obviously I wouldn't mind him liking funny/decent pictures of his friends (although he doesn't seem to do that often). No, these look like glamour models - they are wearing loads of makeup, sexy revealing clothes, and some are in quite sexy provocative poses. I do not of course expect him to stop finding other women attractive, but needing to actually push that button, to broadcast that fact and let the person know? Do you think that is going too far?