I don't believe that non-monogamy should be used to save marriages at all.

Both my personal experience and popular non-monogamous wisdom say that opening a monogamous partnership is the fastest way to expose any cracks that are there. It's way more likely to tear a broken marriage apart than fix it.

Had my husband not been receptive to the idea of swinging, I would have happily remained monogamous forever. I'm glad I've had the opportunity to explore other sides of myself, and I don't think that I would want to return to monogamy at this point.

The point is, if a couple is going to choose to become non-monogamous, they need to be at their absolute strongest point ever.

If they can't do that on their own, then non-monogamy won't save it.