None of us is like the other
For me, the improvement started after the third treatment in the first round. I had to have rounds of PE repeated frequently, spaced at about 2 week intervals. That was until we tried a combination therapy of PE, steroids, and Imuran, later dropping the steroids. Eventually, I was able to go to three treatments every six weeks. I had a change in work schedule that made it easily for me to do one treatment every other week. Overall, it is the same number of treatments, just spaced differently. The combination therapy keeps me stable and functioning well, if not ideally.
However, that is my own experience. Yours will likely be different. It is possible that PE will work very well, with nearly instant improvement. It is possible that after the first round, you never need another treatment. I hope that is your experience. One the other hand, it is unfortunately possible that it will do nothing for you or that you will only get at most a few days of good relief before you need the next round.
By the way, Took’s description is mostly accurate in a very funny way, but it has one aspect that is just not true. The plasma does not wait to be recycled into the next patient. It is discarded as medical waste. I suspect why Took could not move much during his PE was that the catheter ended up against the vein wall, rather than precisely in the middle. Movement then presses the vein wall and catheter together, restricting the flow. I don’t know why Took needed the strong medicine, but I have never needed to take any medicine after a PE, and I suspect you won’t need to either.
The blood pressure issue could be a bit of a problem for you because you already experience orthostatic hypertension. One solution is to eat a salty snack or drink some broth at the start of the last bottle of plasma. The salt will help kick up the blood pressure. Another option is to have the nurse infuse some extra saline. That will raise the blood pressure.
Godspeed with the treatment,