I think cartridge life depends a lot on how heavily it is used (i.e. how much debris it gets and how often it needs to be cleaned). I've got on over-sized 4-cartridge filter that I only need to clean once a year. It's a pain to clean, but is cleaned less frequently. I was able to go around 6 years before replacing the cartridges and that was only because of some broken straps which I suppose I could have glued back together.

My pool has a mostly opaque electric safety cover so the pool does not get that dirty, though the cartridges certainly are filled with dirt, oils (lotions) and cedar needles after a season.

I would think that you could get more than 2-3 years out of a cartridge.