Which is preferrable::
Get married, have children, 'cheat', then divorce ...or...be honest with yourself and your partner and admit that the possibility of loving more than one person during the course of a relationships life cycle is part of the 'facts of life" ? Why do we continue to accept the religious view of marriage to mean one man and one woman FOREVER? Who believes in forever anyway. Can anybody know for certainty that feelings, thoughts or personalities do not change with time?
Why do we subscribe to this religious dogma?
It's not wrong to love more than one person at the same time, but it is wrong to cheat -- and by that I mean being involved with more than one person when you're supposedly exclusive to at least one of them.
Some people can share sexually and/or romantically, some people can't. Everyones needs are different and there's nothing wrong with that. We do need to be honest with one another tho, if for no other reason than it makes life easier, and we particularly need to be honest about things that have a strong emotional impact.
So yes, it's preferable to be honest immediately about your own needs but you'll have to accept that in a society that at least gives a lot of lip service to the value of monogamy that will be limiting your dating pool.
I don’t think anything’s forever, but if you can’t trust the person your with, then don’t stay in the relationship. If you feel that you need something else, go to your partner, be honest and move on. No one seems to have the balls to be just honest.