It's been 20 years, should I just let it go?

Sorry long post...I'm know in my heart that I'm most likely being irrational and stupid. My wife and I have been married over 23 yrs, together for over 25 yrs. Like most marriages we've had our ups and downs. However, I think our ups greatly surpasses our downs. We have 4 children together, ages 8,11,15, and 19. We both are successful professionals and have a great life together. You're probably wondering why then am I posting here?…which is a great question. I've been lurking on this site now for quite sometime, reading post of others in hopes of affair proofing my marriage. There have been no suspicions or red flags, just thought that I would make sure that I do what I can to make the best of our marriage. Now, getting to the crux of my post today…20 years ago when my wife was doing a lot of traveling for her job, she was assigned to a project that kept her in Hawaii for 3 months. During that time we were having some arguments, mostly about the amount of travel her job required. Anyway, I went to visit and stay with her for a week after she'd been there a couple of months. She seemed a little distant, but I just attributed that to the issues that we were dealing with. At that time I didn't see or sense anything out of the norm. Fast forward a couple of months after she returned from her trip, we had recently moved to another state where she would be permanently working out, which meant no more travel. Things were really going good for us and we were getting along famously. One evening she asked me to attend a function with her that I didn't want to go to, I'm not sure if it was guilt or what, but she kind of jokingly said that her friend would have taken her. I enquired as to who this friend was. This is when she told me about her affair while in Hawaii. She said that they had not had sex but that they had kissed and it was over. She was not in-love with this guy and wanted to be with me. I repeatedly questioned her about the extent of the affair, but she always and still says that there was no sex. We were really young in our early 20's and had only been married for 2 years. It took some time but I decided to stay with her and make a life with her. It took years to get to the point that I could fully trust her again. She was remorseful and did all that I ask and still does to be open and transparent with me. I truly love this woman, even if it's not the way that it was prior to this incident. Now to the crux of my issue and why I'm posting my story. As I've mentioned, I've been on this site reading a lot of post. It appears that there is a common theme where WS tells the BS that the affair only consisted of a kiss, only to be informed by the veterans on this forum that it was probably much more and later discovered through FB, Text, email, that sex was indeed part of the affair. Unfortunately, during my time, we didn't have all of these tools to catch a lying spouse. All I had was her word to rely on. Now to my question, at this point, after all of these years, should I even care? She's been a model wife for the most part for over 20 years. If it went beyond kissing to making out with petting and fondling minus the act of sexual intercourse, does it matter now that I have already decided to reconcile and have created a family with her. If I were to discover that it went well beyond kissing, should I say that this would have been a deal breaker for me then and I should no longer feel obliged to continue with our marriage? Or am I being a douche bag and should just let it go and move on and enjoy the life we've built? You guys give really insightful advice and I would be greatly appreciative of some good counsel from you learned posters.

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