Hmm... There are added layers to this situation that spike the eroticism, and the tremendous appeal. In view of the loving husband's candid revelation concerning his very frustrating condition, there is an unselfish nobility in reaching out to this couple, and to this very alluring wife. Clearly, it was his predicament that drove them to this kinky lifestyle in order to satisfy her carnal needs. Even with full knowledge of the causes of Erectile Dysfunction, sometimes a wife may privately curse her own inability to sufficiently arouse her mate to the extent of overcoming the problem by sheer will alone. In essence, as horrible as the husband feels, she may inwardly be beating herself up. And this can lead to her feeling less of a woman just as he feels less of a man.
Enter: the sexual surrogacy of the swinger lifestyle, with the added kink of the cuckold/wife-sharing fetish. The medical issue isn't solved, but the overall problem is for the wife, and for the couple's sex-life. They are astutely eliminating the dilemma at no financial cost to them, and with a much lower risk of any emotional entanglement ( as there would be with an extramarital affair ). With so many eager male volunteers willing to service her, the wife's self-image is given a massive boost. And the husband experiences a boost in pride because of all the horny men ( with all their sustained rigid erections to salute her ) proving how hot his hotwife truly is, and always was, without question. And thus, this sort of lifestyle rescue is an example of how it can benefit marriages, along with bringing a welcome spice.
Fucking happily-married women in the swinger scene is already a major turn-on. Lending my hard dick to a just cause adds a very pleasing dimension to all the beautiful, euphoric adultery. If only we lived closer. It would be such a thrill to service that super-sexy wife on a regular basis, several times daily.