the DH was remorseful, stopped the affair, they repaired the marriage and he has never had another
Sorry but this is utter crap. A repeat cheater WHO BOASTS ABOUT IT AT WORK is never going to change. It's hard wired in their DNA.
What most likely has happened is this he had a shock when his wife found out, for about 3 to 6 months he was in a remorseful Self-interested "don't want to lose my family" zone and managed to keep his cock in his pants until everything settled down. After that, having learnt his lesson about spouting off and the risks of OW contacting people he knew, he is now more careful about it.
I've been in this situation and men who are determined to have affairs can do it very easily if they want to and do it undetected. All that is required is a bit of strategic thinking and an affair partner who fits into what they want.
For example, to hide an electronic trail, set up a single email account you both have access to and communicate by altering a draft email. That way no one knows about the email account and no emails are actually sent.
Meet up for sex during the day when it is easier to lie about where you were. If the man is self employed this is very easy. If he is not, everyone has a lunch hour.
You would be surprised at the creative little ways a man on a mission can come up with.
I would stake a massive amount of money on the fact that the man you speak of OP is actually still having affairs or if this is very recent, will do and will just be hiding it.