No one can tell you when the fight for your wife is no longer worth it except you. I know it gets old (hell, my husband told me he was sick of it plenty of times), but it's up to you whether holding out is worth the suffering.
I had a fairly rude and sudden awakening. And when I finally hit bottom, it just occured to me what I stood to lose. The recovery and return to my husband was far from fast or easy, though. We still fought, battled mistrust. He got really unhappy whenever I got e-mails from ANY guy because he didn't know if I was reverting to my old habits. I got sick of constantly begging him to talk to me, to open up. It's really hard to work through all of the knots I put in place. But it really can be done.
A big thing was that I was very honest with my husband about how I still felt about my OM. Just because I chose to end the PA didn't mean I could shut off the emotions as easily. They had to die their own natural death. To that end my husband never asked me not to talk to OM, or even not to see him. But I promised never to do either without his full knowledge. It helped a lot. And as I said, the emotions died in the light of reality. Every time OM talked to me I felt less until now I quite happily tell him to go to hell. After his obnoxious call last night I think I can finally ignore his calls altogether without feeling any guilt.
Unless your wife obviously goes back to the OM, it really is over for her. She's just working through the aftermath. Remember, the affair seemed just as real as your marriage at one time, and there is some grieving she has to do for that relationship, even if it was based in fantasy.
The grass may be greener, but then again, it may also be astroturf. ~Amy C Brown