It's much better form to talk about it up front. I have a pretty hard bottom-line rule, that if you engage romantically with someone else without discussing it with me, that's cheating and I'm done. That's been my rule all my life; though before poly, I'd likely have been done had you discussed it with me.
That's another cool thing about poly. You and your wife get to decide with each other, what cheating is for you.
Love is that condition in which the happiness of another person is essential to your own...
Robert A. Heinlein
Me: female, bi, (formerly hinge of a vee)
with FirstBoyFriend (FBF)(moderately long-distance)
and no longer with CurrentBoyFriend (CBF)(who lives in the apartment building next door)