The longer your session is, the more exp you get. Premium poses seem to grant more exp and the difference in your levels is important, too. It is said that the hotel rooms give a bonus as well.
If you do it with one person more often though, you get less and less exp from him/her.
If you do it with one person more often though, you get less and less exp from him/her.
Relax, it's just a bunch of chicks taking a hot bath