I definitely believe that if you're relationship is such that you would consider sleeping with another person then it is time to end the relationship before moving on. Having had a few opportunities present themselves to me though I certainly have some empathy for those who make these choices.
Ah never mind, I see from the answer you have left below that this is something you feel strongly about. Fair enough. I was just a bit thrown because getting a notifcation about something from a while ago is like if someone came up to you in the street and just continued a conversation you'd had with them a year ago. You'd probably be confused.
I stand by my answer because in the very unlikely scenario I imagined (with the spouse in a coma for many years like something out of a fairy tale) they would be to all intents and purposes dead. I think expecting your spouse to go without companionship and love for many years in your absence is a pretty tall order, so if they were very lonely and someone came along who could give them a chance at happiness again I think it would be understandable to take that chance (and I'd want my husband to be happy under those circumstances).