Honesty vs. ?

It seems that most of the time in relationships, arises spontaneously and unpredictably. Any previous logical discussion about it destroys the pion and heat of the moment, but there are certainly issues that might be better sorted out beforehand. For example, it might be important to discuss whether both partners see the as signaling a turning point in the seriousness of the relationship, or whether it is simply a "friends with benefits" arrangement; partners might also care to know about previous ual histories. Naturally, this works both ways--if a guy wants to know about a girl's past partners, he should be willing to reveal his own. But when should this sort of honest discussion occur? When two people are drunk and ready to go for it? Or when they wake up together the next morning?