Is there EVER an end to the selfishness? Is there EVER a point where they get grow up?
Possibly. With the help of therapy, I suppose.
On their own... . meh, I think the selfishness is just a part of who they are. They're consumed with what's in their own head/mind that I doubt they notice what's going on in the outside world.
What you said about the non-partner put in a no-win situation or having the give an immediate answer, is exactly what I'm going through now. My BPD bf and I have plans to get together this weekend. I planned to drive down today, however, I had to move it back a day (tomorrow). Due to the issues of the cat having to go to the vet (her eye just started bulging out. Noticed yesterday), the car leaking oil, the air conditioner going out on the third floor, and the garbage disposal in the kitchen sink breaking and the sink not draining. Everything kind of fell apart all at once (I'm sure you all have experienced something like this at least once in your life time).
So, he's bawling me out about how this is probably stuff I should have taken care of months ago. A non BPD person, would have most likely been understanding. My BPD bf, yeah, not so much... .