I wouldn't say they lose it. I have only been with my husband for 2 1/2 years, and I will admit there are times where the passion just isn't present as much. Sometimes for a few days, sometimes a week, or sometimes even months. But it always comes back. That's what is important. You have to keep your relationship ALIVE!!! You know... like switch up the routine a bit. Have a wild, erotic night every now and then. Let him do something you've never done before. I also think that guys may think of other girls while having sex, but... they would never admit to it. And if they did, then that's wrong!