I went inpatient 3 years ago for a total of 3 weeks, but it was a regular psych ward in a hospital, and they thought it was just a depressive phase of bipolar disorder at the moment (...) (I don't have bipolar, but it was my diagnosis for 10 years).

What I can tell you is that one of my best friends went inpatient in a clinic specialized on BPD for 5 months - in the beginning she just wanted to cry and get out of there, she told me it was horrible, but now she speaks very highly of it and says it saved her life, which I believe is true, knowing her issues and seeing how she is now.