It isn't right to think any person is irredeemable. I know that a man can be so stunned by the misery he caused that he never lapses again and can turn things around.
My husband had a long affair which I discovered. and we were both in terrible turmoil for a long time. It helps me to remember that I am not perfect either.
That was 25 years ago. We saved our marriage and that was because we still loved each other. We are so glad we made that decision.
To quote from Hilary Clinton's new book,
"
“There were times that I was deeply unsure about whether our marriage could or should survive, but I asked myself the questions that mattered to me: do I still love him? And can I still be in this marriage without becoming unrecognizable to myself – twisted by anger, resentment, or remoteness? The answers were always yes.”
So yes people can become non cheaters after a bad lapse. If you both sincerely want this. But to quote another woman,
"The screwing you get is not worth the screwing you get"
(Dorathy Parker.)