Is swinging a sustainable, long term sexual lifestyle for a couple?

Sorry, I should have typed “provided I marry that person”. I think y’all understood what I meant anyway.

[Hal Sparks]
I have no problem with wife-trading, as long as you’re trading UP.
[/Hal Sparks]

A good friend of mine and her husband have been swingers for several years. They don’t make a frequent thing of it, though. A few times a year, at most, and the majority of their activity consists of inviting a mutually agreeable 3rd party into their bed. It seems to be working well for them, with a (to date) minor bit of conflict regarding female 3rd parties. Wifey is apparently excessively picky, in hubby’s opinion, regarding female 3rd parties. Essentially, it seems, she doesn’t like them to be prettier than her. Hubby is more easy-going about who wifey wants to invite on board. Anyway, they’ve been at this for ten years or so and seem to be doing okay.