My own "wayward" knew full well what it would do to me if I found out. But just as the relationship seemed to matter little to her - so to was her feelings about what it would do to me.
She knew the damage it would cause to me - considering my past (which she knew about) - and especially with me dealing with depression (which she also knew about) - the man who she claimed was "The Love Of Her Life".
I stupidly also use to consider her "The Love Of My Life" as well.
I even asked her on "D-Day" if she realized how it would effect me if I found out - and she said "yes". But she did it anyway - for two weeks before I discovered what was happening.
As we discussed things after "D-Day" - and during the time when she still wanted me to forgive her - she said it was a "little shit thing" - a "spur of the moment" event. She tried to minimize it as just something small and only lasting a split second in the grand scheme of things.
It lasted for two weeks before I found out - and appears to still be "lasting" one month later after "D-Day" (today being the one month anniversary of "D-Day").
It can continue for as long as she wants now since her and I are done. She is a six hour flight away (and apparently taking up permanent residence) from me so I will never have to see her again.
Frankly cheating is a selfish act - done with the hopes of never being found out - so it can continue and be an endless source of gratification to the cheater. No doubt their egos need to be stroked that bad.
In this day of computers - not getting found out is harder to accomplish because many are not very computer savvy - and eventually will make a mistake - and someone else will get their heart shattered when they find out their loved one was not the person they thought they were.
Cheaters walk on roads paved with broken hearts.