My now dh cheated on me once before we were married, an yes it wa more than kissing. We were living over 1000kms apart, he decided to go to the pub for tea on his own, then because the footy was on stayed to watch that with a beer, then it got more crowded and he kept drinking... Ended up taking some girl home he didn't know, didn't have a condom, so didn't have sex but she did things to him... Then he freaked out and told her she had to leave NOW, she was shitty in the least.. Then he rang me at 4am crying and telling me what he'd done.
He hated himself for it, literally hated himself... He cried and was scared of losing me, an I told him if he was serious about us he had to move to Adelaide to be with me.. And he was there within two weeks. He proposed as soon as he saw me. It sounds like a really bad time to propose doesn't it... Haha!
BUT... I almost almost almost dumped him over it. This is what it took for him to realise he was genuinely terrified of losing me and that he wanted me forever. I cried and talked about it no end, it made me insecure for a long time, but in the long term.. I knew that whatever happened in our lifetime he would be honest with me. He could have not said a word and I'd never have known. We were living in separate cities, the girl was an overseas traveller who knew none of our friends, and yet he chose to tell me. I could also see that he regretted it so much that I was confident it would never happen again.
It made us stronger.. It taught us about communicating through conflict and it taught him a big lesson.
So no, not always. Its a very individual thing though. If he cheated twice though I would expect that he didn't learn the first time and therefore never will. My husband used up his one and only chance, I'd leave if it happened again.