You know marriage is very complex relationship in today's world. No matter what, both are human and both can't deal with a fact (not for log) that someone they are being intimate with was intimate with someone else. So why play with the fire, keep your ex life in a safe deposit box and lose the key...
i agree...it's best not to dig up old graves.
however, in todays world...there is a thing called sexually transmitted diseases. if he was promiscuous then he should either have good enough sense to get tested (and make sure he is clean) or tell his potential partner about his promiscuity so she can make an informed decision about whether or not she wants to pursue a relationship with him.