I can think of a couple of concerns about this approach. If we have empathy for our pwBPD, we may not find it respectful to intentionally expend their energy on a fruitless argument. It does not seem likely to build trust. Another concern is that banking on our pwBPD running out of momentum can be a losing game. Mine can go for hours. I find that carefully conserving energy and working on boundaries has had better payback.
WW
I absolutely agree with this WW. If you just try to wait them out, then you are doing yourself a disservice by continuing to listen to it. You get to place yourself in a situation where you continually hear the negative, mean things she says to you. By using boundaries, you reaffirm what your values are and regardless of what she says, or does, or behaves, you are in control of your own emotions, behavior, reactions, etc.
As an example, my H used to rant for hours at a time at me and I just sat there and took it. I would try to justify myself, cry, and eventually apologize and agree to everything he ever accused me of. When I began to look at my own weak boundaries, I realized that I would not allow any other person except my H to yell at me and rant at me that way. I would get up and walk away. I saw that I needed to hold myself to the same standard with my H that I would with a stranger.
So with all my resolve the next time he began to yell at me, I mustered up all my courage and said "I don't like to be yelled at. I'm going for a walk." And I walked right out the door. Came back 30 minutes later and I still heard my H yelling inside at no one. This reinforced my understanding that I cannot control his behavior, only my own, and I remained outside for another 15 min. After he saw I was outside, he came out, calmed down and we had a conversation. He told me he was upset that I walked out and I told him that I wasn't going to let myself be yelled at like that anymore.
He tried it one more time, and I responded exactly the same. He doesn't yell at me now. He knows that if he yells then he loses my audience. He knows that he is left alone in the house by himself with no one to witness his tantrum. And what's really neat, is that now when he starts to feel himself getting frustrated and angry with me, HE is the one who goes to take a walk to calm down because he wants me to hear him. He knows now that he has to get himself under control so we can have a conversation. HIs behavior change was not the goal of my boundary. It was to remove myself from being yelled at. HIs behavior change was just a natural consequence of me not letting him treat me badly.