Plates and FWBs are easy. You don't invest anything and so it literally does not matter.

But what about OLTRs, MLTRs? Poly relationships? Any situation where you actually do invest to some extent. And yet you know other men are fucking her.

Is it just a matter of having enough women on deck? The few times I've had multiple girls in concurrent rotation it certainly seems easier to care less about your competition. But as soon as you are down to 1 chick.. and know that chick is fucking other guys.. it seems impossible to hold frame.