I'm suspecting that, since the old plaster was in a pretty deplorable state, every time I brushed or vacuumed I was probably sucking in plaster debris. I am thinking that the plaster was constantly breaking down (also it was a constant battle with algae attacking all the pock-marked and worn areas on the bottom - it sort of looked like a coral reef down there). I experienced filter pressure increases nearly every 2 weeks or so, but so far this season with the new plaster the cycles are much longer. I cleaned the filter a month ago (I never just backwash....rather I take everything apart and hose off the grids, clean out the tank, pump strainer, etc.) and I'm still at the same pressure that I started with after adding new DE.
What is the 'average' filter cycle length - if there even is such a thing? I do think that what I was experiencing with the old plaster - that of having to clean the filter every few weeks - was probably a bit excessive. Is it possible that now I might only need to backwash following a pressure increase and then take the filter apart every few cycles instead of at every DE change as I have been used to doing? Anyway, I'm loving the reduced level of maintenance! Plus the water seems so much cleaner and fresher (well, for one thing it was a fresh fill only about a year ago).
Also, I have a question about leaving the grids in while away on vacation. Before the renovation, I always took them out for fear that the pressure would go up too high while I'm away from the pool for a few weeks. It's probably not an ideal way to run a pool since without the girds I'm basically just circulating water (and yet the water never looked too bad after I got home from a trip) But now since the filter cycles seem like they are going to go much longer, I was wondering if I'd probably be ok cleaning it good before leaving, adding new DE, and then just keeping the filter running with the girds in?