First of all, Good luck with your testing. I hope they find something wrong and are able to fix it. When I had my first tilt table test, I was up for an hour. I'm not sure if that's considered prolonged or not, but it was longer than most of them. I didn't pass out, but my body showed signs of POTS. When I had my second one, I was up for about 40 minutes, and I didn't pass out. My docs said they couldn't find anything from either tilt table, so I was sent back home with no answer. It wasn't until 2 years later when I saw Dr.Grubb that he told me both of my tests showed I had POTS and NCS. But when I was there he did a mini-tilt, and I had no BP when I stood. That time I failed the test, so he concluded that my autonomic system only fails some of the time.