In order to recover, he needs to agree to never ever be in contact with her FOR LIFE. Contact should end with a no contact letter patterned after the one in Surviving an Affair:
Dr. Harley's (From SAA)
(OP), I want you to know that out of respect and love for my wife and children, I have come to realize that I must never see or talk with you again. My relationship with you was a cruel indulgence that (BS) did not deserve. While I cannot completely repay (BS) for the pain I have caused her, I will do my best to become the husband she�s been missing. I care a great deal for my family and I would not want to do anything to risk their happiness. I will not make any further contact with you and I do not want you to make any contact with me. Please respect my desire to end our relationship.
Sincerely,
(WS)
Dr. Harley's views on ending contact:
Dr. Harley in Coping with Infidelity: Part 2
How Should Affairs End?
Never see or communicate with a former lover
Once an affair is first revealed, whether it's discovered or admitted, the victimized spouse is usually in a state of shock. The first reaction is usually panic, but it's quickly followed by anger. Divorce and sometimes even murder are contemplated. But after some time passes (usually about three weeks), most couples decide that they will try to pull together and save their marriage.
The one having an affair is in no position to bargain, but he or she usually tries anyway. The bargaining effort usually boils down to somehow keeping the lover in the loop. You'd think that the unfaithful spouse would be so aware of his or her weaknesses, and so aware of the pain inflicted, that every effort would be made to avoid further contact with the lover as an act of thoughtfulness to the stunned spouse. But instead, the unfaithful spouse argues that the relationship was "only sexual" or was "emotional but not sexual" or some other peculiar description to prove that continued contact with the lover would be okay.
Most victimized spouses intuitively understand that all contact with a lover must end for life. Permanent separation not only helps prevent a renewal of the affair, but it is also a crucial gesture of consideration to someone who has been through ******. What victimized spouse would ever want to know that his or her spouse is seeing or communicating with a former lover at work or in some other activity?
In spite of career sacrifices, friendships, and issues relating to children's schooling, I am adamant in recommending that there be no contact with a former lover for life. For many, that means a move to another state. But to do otherwise fails to recognize the nature of addiction and its cure. <snip>
We don't know if R.J. still sees his lover, but he says he has broken off all contact. In many cases where a person is still in town, that's hard to prove.
But one thing's for sure, if he ever does see his lover, it will put him in a state of perpetual withdrawal from his addiction, and make the resolution of his marriage essentially impossible. In fact, one of the reasons he is not recovering after three months of separation may be that he is not being truthful about the separation. Entire article at:
http://www.marriagebuilders.com/graphic/mbi5060_qa.html How to Survive an Affair chapter in HIS NEEDS, HER NEEDS
p. 177
...I have seen husbands build new and wonderful relationships with their wives but then go back to their lovers after five or six years of what appeared to be marital bliss. When I ask them why, they inevitably tell me they miss the woman terribly and still love her. At the same time they stoutly affirm they love their wives dearly and would not think of leaving them.
I believe a man like this has told the truth. He is hopelessly entangled and needs all the help possible to be kept away from his lover and stay faithful to his wife. I often recommend that a man once involved in an affair come in to see me every three to six months on an indefinite basis, just to talk about how things are going and to let me know how successfully he has stayed away from his lover.
He must resign himself to a lifetime without her. HE MUST CERTAINLY NOT WORK WITH HIS FORMER LOVER AND SHOULD PROBABLY LIVE IN SOME OTHER CITY OR STATE. Even with those restrictions the desire for her company persists... 
