While I don't have the Seachem literature in front of me, I remember reading that supposedly it does NOT leach back into the system when "full".
Chase33 - I'd just run with the Purigen only after the AC
is exhausted. I took out my AC
"cold turkey" and switched to Purigen only almost two months ago. I haven't noticed anything bad happening. My water parameters were perfect before, and they're perfect now, so no real proof there. But I can say that the "slick" on top of my water has dramatically decreased (and is just plain nonexistant some days) since using the Purigen.