Any tips on how to ride your man?

I don't mind being on top, but after a while my thighs burn so bad its not even enjoyable anymore. But usually once I stop, the sex stops. He won't flip me over and continue. But if hes on top and wants me to continue on top later, I don't have a problem with that. And he's a very giving partner in every other sexual aspect. I just feel like he gets disappointed (but won't say anything) that I'm not like some crazy porn star who can ride him hard for a long time or something.