I used to think that, but under our current system, I don't think there are any long termers.
To have women that behave over the long term, the man needs to be supported by society and by law.
That could be. Maybe by nature, we are not monogomous.
Just a guess, but probably most women want a long term relationship. It is in their nature. It is programmed. Has to do with the benefits of a relable mate when raising children.
Males on the otherhand, have different goals. Procreation with a lot of females means more offspring.
So, men have to be taught to be monogomous. To overcome their nature. This is done by society, law, the parents and extended family, and most importantly the women themselves.
The free sex and feminist movement has taught men that they can get what they want without any commitment. For women, there is little or no risk of getting pregnant so they are less inhibited. However, women still retain that desire for commitment.
Anyway, it seems like a cold, cruel, and sad life to never have a long term relationship. Worse for the children if there are any.