Your friend deserves all the sex he can get from your wife, so she can become fully addicted to extra-marital sex. The more often he bangs her, the deeper she will slide into the lifestyle, and the greater her confidence and self-esteem will grow. The day will arrive when two cocks are not enough, and she will "branch out" and take more lovers as she discovers their "availability".
Accept in your mind that she will form attachment to her lovers, because they are giving her their fullest atention. At times, she may feel hopelessly head-over-heels in love with them. This is to be expected.
As long as you continue to be a very understanding, supportive husband who shows no jealousy, and installs no curfews, and shows her proper respect, encouragement and appreciation, your marriage should remain strong (or get even get stronger).
Cuckoldresses change their lovers quite often, so you should not get unduely concerened about any particular lover. A guy who is the flavour of the mouth at the moment, can become history if he tries to control her. She can flick him into the past as easy as changing the wallpaper, if he no longer pleases her.
Whilst it is true that she could flick you off with divorce, she is most unlikely to do that, because if she marries someone else, he won't tolerate her thirst for more than one cock.
It is far better to stay married to her cuckold, so she can have any cock she wants.
(Cuckold husband = any cock she wants)....wow.....wow....wow.......YES SIR.