Depends totally on the honesty and openness of each of the three.
It only takes one to ruin even a monogamous relationship, let alone a three way.
Why do you think there are so many monogamous divorces? 🤷🏻♂️
Simply no honesty in today's relationships and little willingness to talk things through.
I have actually known threesomes that have been together for over a decade.
They didn't hide anything though and they talked to each other. Not argued.
Today you can see how a relationship will work, simply by how many they have blocked!
The bigger the block list anyone has, the less likely ANY relationship will last. Monogamous or polygamous.
No willingness to talk it through, so it's easier to block. Don't like your partner? It's easier to divorce!
Yet how can anyone be open, if they just simply cut you off? 🤷🏻♂️
This is what this society has done to even monogamous relationships.
Polygamous relationships you simply can not own any of the others, nor can you ignore them or endlessly argue with them.
And it's no different in monogamous relationships.
Now start arguing out loud with yourself and see how long you stay out of the looney bin! 🤷🏻♂️🤣
The ultimate in a asexual or aromantic relationship! 😈
For anyone that really cares.
Yes I have been in such a MFM relationship. It lasted six months before the dishonesty was revealed. And was basically the end of the relationship for all three of us. 😞
That all depends on the personalities involved, agreements they made, and whether they respect those. Without further details it could be anything from a few minutes to a lifetime.