This is something that we don't have to deal with. My wife and I have separate beds in separate rooms, so our beds are ours alone and we can share them with whom we please. We don't have issues with sleeping arrangements.
Shortly after we got together several years ago, my wife had an issue briefly over the idea of somebody else having sex with me in our apartment. I pointed out that any place I can't freely have company is someplace that isn't my home, so to solve the problem I told her I'd find us adjoining apartments somewhere and then she'd never have to worry about that and I would actually have a home.
She decided she'd much rather live with me than next door to me and worked through her issue. I suspect it had to do with not wanting to have to clean an apartment by herself....
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.