Regular sex is important, but regularly switching sex partners isn't really how I want to live my life. I don't want 50 lifetime partners, 38, 15, or even 12. I wanted one. That I have more than one is a sign of failure of a relationship each time, which is not a success.
If I had my choice, I'd:
1. go back to a 1930-style relationship, were I would have married early and stayed together.
2. We'd have clear roles, although not the sexist, dated ones from 1930. I'm very flexible, so I don't much care what they are. I just don't want conflict over who does what, re-negotiation of everything, and clear roles eliminate a lot of room for conflict. With some permanent, clear division of responsibility, we both know what's required of a good partner, and if each of us focuses on that, things work out.
3. As a cultural norm, divorce would only happen for fault (abuse, infidelity, etc.). Both sides would try to be good spouses.
4. Extended families would live together and support each other (which also keeps an eye on things not going south).
I'm not trying to impose that on anyone else, except for a research methodology to account for people like me.