If I found out my husband was having an affair I'd pretend I hadn't. I can't face the disruption at my time of life, I'd prefer him to go on acting as if everything was normal. Once they know you have found out, they either move out completely, or they stop pretending everything is normal and start staying out more. I wouldn't want my husband saying to me "sorry I won't be here at xmas I am going to spend it with <insert lovers name here> house this year." I'd want him to go through the motions of having a normal xmas with us, even though he might be wishing he was elsewhere. Or, worse still, "Sorry I can't pay to have that new patio laid, I promised <insert lover name> I'd get her a new car". I'd want him to feel he'd better pay for the patio so I didn't start asking where all his money was going. Oh yes, if you don't tell him you know, then all the cards are still in your own hand.