In my (finished) marriage there was quite a lot of behaviour I put up with, that would have mumsnet saying "LTB!"
Talking to friends, family there seems to be a lot of it about in their marriages too. (Not gender specific, things like financial control, secret drinking, debts, cocklodging, contempt, verbal abuse etc etc)
I think most marriages/long relationships have elements of LTB behaviour- but I don’t know if my perspective is warped.
Putting on voting to allow people to be semi anonymous, as I expect the comments to be full of very happily married types saying IABU 