Infidelity/cheating

I've been married almost 2 years. We haven't had any issues with cheating so far. I joined at a group at my church  for married women. Almost all of the women in this group ( ages range from 30-70, I'm 26) have dealt with infidelity with their spouses in one form or another. All of them have been married 10+ years. The infidelity always, to them, happens around year 5-7. How common is cheating? Have you ever dealt with your spouse cheating? If so, how did you guys work through it? Would you leave if he cheated for the first time? Would you stay if it meant longtivity? Is it really in a mans nature to want/be with multiple women? Even if it's just sexually?