Thinking of wife having sex
When I asked a cute blonde girl out when we were in college, I knew that she had already had sex with at least two guys. I knew that because we were friendly and she told me how much she liked them fucking her. After she broke up with the second guy, she asked me over to her dorm room and we had sex. I was at least the third guy that had fucked her and she was my first.
Through the years before we got married I know that several more men fucked her while she was away on business trips. She would tell me about the men that she met while on a trip but wouldn't admit that she had sex with them but also never said that she didn't.
Now many years later most of the time that I want to have sex with her I think about the many guys that have been inside her and it helps me get hard so that I can fuck her. If it didn't arouse me thinking about her other men I don't know if I could always get an erection and would be able to fuck her whenever she wants. So knowing that many other men have been inside my wife works out great as I can always get hard even as I have gotten older.