Hi Lisa,
To answer your question (how long does PLEX last?), you have to understand the plasma exchange process.
It removes the circulating antibodies from your blood but all antibodies are not circulating, some are bounded somewhere in your body.
The filtering process is a continuous one, one cannot thus achieve a 100% efficiency, it depends on on the total volume of plasma exchanged, in France they exchange 1.5 times the plasma volume corresponding to your body characteristics.
The production of antibodies is not stopped, your blood is thus continously re-enriched in antibodies right from the end of the exchange.
Finally, not two patients are alike...
In my case, I have one exchange every 7 weeks...and I started by one every 10 days. I feel the change after 2 or 3 days.
Maurice.