Filter cartridge -- when to clean, when to replace?

[grpools]

We had our first pool installed about 5 years ago (13,500 fiberglass pool, swg, 4 cartridges -- 320 sf) and I have read many of the filter threads and am confused about when a cartridge needs replacing and when it can just be cleaned.

We bought new cartridges last year (based on pool store advice because our filters were 4 years old) but we never got around to swapping them out because we were fighting iron stains and didn't want to mess up the new filters while treating the stains. Now after reading threads here, I'm wondering if we need to replace them yet. Our filters always drop back to the psi they were at when new after we hose them off (I must admit I haven't soaked them for over a year -- the bottle of stripping solution was too expensive but I've now read about using dishwasher powder or tsp -- Thank you!!!). I don't want to replace cartridges that are still working if I don't have to -- but how do you know when to clean and when to replace?

[waterbear]

Rule of thumb, if you have been cleaning and soak them on a regular basis and not ignoring them you can get about 5 years out fo them. If not maybe only about 2. If they are 5 years old I would say it's time to replace them.