IMHO people cheat for variety and excitement and it seldom has anything to do with long term "love". In fact, physically open relationships between mature people where the parties haven't been conditioned into reacting to every dalliance as some kind of nuclear meltdown betrayal can be quite healthy, but only where there is a deeper trust and the maturity to understand that there is a difference between a life long companion and an occasional fling because that contributes to your enjoyment of life. In fact, if your long term relationship can't withstand something like that, then you probably shouldn't be in it in the first place. Let's face it, relationships will become physically boring after enough years so why must we put ourselves in some kind of sexual jail for the rest of our lives just to comply with some social construct of physical monogamy. Jealousy is only an issue if your relationship is not strong enough, in which case maybe you shouldn't be chained to each other anyway.