I tend to be a page turner until I hit a brick wall and have no choice but to close the book. (This means the other party has decided to close the book.) Even then, I keep a bookmark in place.

It has to be up to each individual in a relationship; where do you draw the line, say enough is enough? I'm not a good one to answer that, except for myself. I still maintain relationships with my formers, so even though there may have been times I closed the book, I only set it aside for the furture. I took a break and rested my weary eyes. Often, I could later focus more clearly, as could a partner, and the book was reopened. I am thankful for this and it is to no credit of myself; I actually think it might be a flaw in me that hangs on till the last breath is breathed...literally.
I tend to be faithful and forgive (eventually) as so many have done with me in the past. I dislike conflict and confrontation, so I look for ways to avoid such things. Maybe not the healthiest way to handle a relationship, but I am getting a little better at it.
An interesting observation: I used to be a cat person, loving them for their independence. Over many years I have become a dog person, loving them for their faithfullness; this mirrors how I have changed over the years and may account for my page turning. Not sure if that is "growing up" or just getting too old to fight anymore.
In any event, one must determine where his/her boundaries are and whether or not those can be tested, pushed, explored, manipulated, etc. Some things just aren't worth closing the book over, but I think deep down, we all know when that time comes, if it does indeed come. It is never easy, but likely offers relief. Maybe when you close the book, it was just a short story and you finished it. All things come to an end and it does not have to be a bad thing. Often it is liberating and maybe even exhilerating, as if a load were taken off our shoulders.
Does anyone else have any thoughts or experiences they'd like to share? I know this is an old topic, but feel it is important to discuss.
Hope all are well and turning the pages, happily!
Bud