My best friend (M40) is in love with his girfriend (F36) I can tell, I know him very well… however, as we are very close and confident, he keeps pointing out to me how beautiful or hot he finds other women, sexually speaking. He does not cheat on his girlfriend (as far as I know) but I wonder why he behaves like this… are men trully aroused all the time despite of being in a serious relationship (I mean, constantly feeling excited about other girls)?