marriage is a huge commitment. something that should never be broken. but unfortunately has been destroyed in the modern day of divorce. however i still feel that marriage is very sacred and should only be for the strongest form of a relationship.
that being said, i think a strong relationship is based off of trust and understanding of each person in the relationship. if you could trust in your significant other enough to find a way to NCMO with someone else then i think that would be fair. i actually think it could be good for a relationship. especially once you have gotten kinda bored with the a long term relationship. i have generally found that the more people you exchange 'making out' with then the more you learn and that good results come from it. sure, you might end up making out with someone that isnt very good, but then again you might find someone that is good and learn something from the experience.
but now comes the biggest question. could a relationship actually have the trust to allow NCMO.
ive never been married (im in college) and one time had a gf that gave me permission to partake in NCMO (or sorts, never heard that actual term, but yeah) i thought it was great, the girl i was dating said it was ok, but eventually admitted to not liking it very much. its hard in a relationship, you might want to have your significant other do anything to let them be happy, but in reality it just might not be the best. hard to say.