100% agree. As long as you have an open dialogue with your partner, there's really no reason for it to ever grow boring.
I think I'm like the bulk of people who would never want to share my partner. Call it jealousy, but I think it's unnatural to enjoy watching someone else touching your partner. Maybe I'm clueless. I also think that when it loses intimacy it's simply f***ing which is not the experience I'm looking for. There's nothing better than engaging in a deep and meaningful conversation and using that as the aphrodisiac instead of having it be solely physical.
But to each his own. I just wish they'd call it swinging/cheating instead of trying to rebrand it.
And I'm sorry, but it will never be mainstream even if some people in my comments claim it is. 92% of open marriages fail for a reason.