This is a tough call but it is yours to make - you and your wife get to make that decision.
Having said that much, I am wondering how "it recently" came your attention and how is that making a difference now?
Secondly, if it was in the past and I am not condoning it, why make it an issue now? just wondering if you left out some details.
Then wondering if you went to alanon, marriage counseling etc. in order to leave the past where it happened.
It sounds like you stayed together for some reason I cannot tell why, but again, it is certainly a difficult thing to go through no matter what the details are.
You came here for a reason and maybe you could let us know how to be more helpful.