We finished our pool in November of 2014. Since we are in Texas, we leave it open year round.
Have a 3hp Tristar Hayward pool pump as the main pump, and a 525 sq ft cartridge filter. I stay on top of the chemistry and haven't had any chemistry related problems as of yet.
I cleaned it not long after the pool was finished because of all the plaster dust. The PSI came immediately back down to the brand new level (right about 20 PSI). The pool builder put the red line indicator on the PSI gauge at 30 PSI. I cleaned it again sometime last year when it was approaching the red line and the PSI gauge came down, but not all the way. It stopped right about 22-23PSI.
Just recently, I noticed that the pool heater wouldn't stay on. You could hear it trying to fire, and then it would go out. I texted my PB and he said that the filter is probably dirty (I hadn't checked because I didn't think it would be time to clean it again). Sure enough, it was borderline 29-30. So I took it off today and they were pretty dark and dirty. So I cleaned them very good, took a long time and got just about every speck of debris out. They don't get as bright white as they used to (some brown stains here and there), but this was a big difference between the before and after.
I put it all back together, expecting the PSI to come back down...but it came down maybe 2 PSI. Its' reading about 28.5.
I turned on the heater, and this time it worked and stayed on. But I also noticed that when the heater is on, the PSI jumps to almost 40 PSI.
I came inside to order some new filters, but just can't believe they would only last 16 months.