If there is an affair going on - which admittedly sounds quite possible - there is a high statistical probability it won't last long ...
How long does it take for a LBS to contract an STD from their cheating spouse?
How long does it take for a fogged-out, fueled-by-a-raging-sense-of-entitlement spouse to drain the family bank account?
I'm not saying that most affairs don't work out (they don't). I'm just putting it out there that there's an awful lot of damage that can be done for every week they are allowed to continue.