I saw stickies for DE filters and sand filters, but not cartridge filters. So I've just recently purchased my house, and the cartridges for my filter (it's a large filter, so I have 1 very large cartridge, then one skinnier taller one that goes inside that one, model is in my signature) were fairly beaten up. They were heavily discolored, the pleats were not held apart well anymore, so they are not easy to clean (half of it you have to spread the pleats by hand to get the grossness out from between them. I purchased some new filters that I installed today (I've already had to clean out my old filters twice due to an algae problem). So now that I no longer 'need' these, I was planning on keeping them as a backup. A friend said he keeps his to open the season each year, then switches out to the newer ones after the pool is clear.
That being said, I'm looking for the best way to clean them. There are chemicals you can spray on them to clean them (the previous owner left a bottle of a degreasing chemical for cartridge filters), I've read that soaking them in cascade dishwashing detergent is also effective, soaking in muriatic acid solution, etc, and so I'm wondering what the best way to do it would be. I'd also have to clean my new ones at the end of the year, so I'd want to get things figured out now and buy what I need for that too.