Just to confirm with Real World Experience, sand does NOT "wear out". Our pool is in it's 41st year and we've replaced the sand once. We did that at the 35 year mark when we replumbed for other issues. No visual difference between old and new sand, no change in performance a'tall when we booted up with the new sand.
Also I've used clarifier to speed things up after an algae bloom, it shortens my clearing time by about a day or two as long as I keep the chlorine high enuf to keep the algae dead enuf. Sometimes company's on the way and we all get impatient! BTW just watch your filter pressure like a hawk when using clarifier so that you don't blow it up.
Update: After almost two weeks of running the pump around the clock, adding a little DE and backwashing when the pressure is up, we can finally see the main drain covers. It's not pristine yet, but it is continually getting better. Man....this has definitely tried my patience! Thanks for the information here and especially the information about the sand!!!!