Seachem claims it does not need to be replaced because the pores are naturally too small for organics to clog, but large enough to be washed to have the old bacteria remains removed. I think it can be rinsed and boiled (several times) to be rendered reusable. I would just avoid the use of any products because of the highly porous nature of pumice stone.
Would you have to boil it? I thought you would just rinse it in tank water (like I would my Mattenfilter) to get rid of any detritus build up?