Your million dollar question answer is, as long as he's emotionally attached to another woman, those feelings won't come back. And until he's ready to completely end it with OW, your marriage doesn't have a chance.
And your question about how long can a LBS last before they've had enough? Depends on the person (I've been at this going on two years since I first got suspicious and for about 16 months since I've had confirmation of my W's PA), but it's not for the faint of heart. There are many days when I'm ready to throw in the towel and get on with my life (like yesterday/today), but everytime I look at my kids I get the energy to continue.
This OW your H is involved with. Do you know anything about her? Is she married?
Hope4us
Me - 49, W 49 S22 & S18 Dday 9/4/07 W claims NC 4/7/08 8/29/09 - Divorce Busted. Lots to work through, but we're going to make it.