Is long term monogamy unnatural for human beings?

[Jenny A]

  Not cheating sexually occasionally requires effort. But not often.

I think I;d have to try pretty damned hard to cheat.  It seems like alot of work, to me.  I;ve got a buddy, great guy..did real nice by his wife and his kids..but, you know..not remotely monogamous.  Everytime he tells me about it all I can think of is how exhausting it must be.

I'm a woman who likes male friends.  Occasionally one of those wants more than friendship.  Actually, that has happened once or twice with female friends.  The difference is the men are sometimes tempting.  But don't picture men falling all over themselves to have sex with me.  It's a tri yearly or so event.