Would you say that there is NO instance in which an LTR can "work out" long term.

Success for the sake of this post equating to...

20 years of monogamy, frequent and mostly satisfying sex, no infideltiy from either side, 15 years of that being co-habitation.

Is this psychologically and biologically possible?

HVM will cheat and leave. HVW will struggle to remain satisfied with anything but a very HVM with his long term game on point.

average and below average men and LVM will beta out relatively early on, leading to loss of attraction by female...

And LVM with LVW will eventually become unsatisfied, or both will become unsatisfied, and eventually lead to mutual attraction loss, and even if they don't cheat or leave, will be miserable long term.