I've had to regularly clean my brakes because of the high mileage I did. Over time I've found that if you do a good job of it they last a lot longer. I take it all apart, rubbers out, wash it with brake fluid, clean the grooves properly, then warm soapy water. The pins, bleed nipple and bolts get wire brushed, I use a brass coated stainless steel wire brush in a drill, they are £3 off eBay for 5 pack of different brush shapes. Pistons are polished with metal polish, if they have rust the polish can't get off I use 1500 grit water paper, dip it in brake fluid rather than water. Then clean the pistons with brake fluid and soapy water. Rubbers are washed out with warm soapy water, not hot water, just warm. Then clean cold water to remove any remaining soap. I spend time with a cloth cleaning out the last grease from the rubbers that might be left. I use air to dry things off too and an old hair dryer (don't heat the rubbers too much.)
Seals are checked, any damaged ones are replaced, greased up with proper brake grease, put them in, thin one first, thick one second (just easier.) Then put some grease on your finger and rub it into the little groves around the seals so that there's grease in there. Put a very thin smear of grease around the outside of the piston near the bottom, the bit that will touch the seals first when you push the piston in. You don't want any excessive grease to get pushed down into the caliper when you fit the pistons so wipe the excess on the seals with your finger, not a cloth. Push the pistons in by hand, they will go in easily, if they feel stuck, you're pushing a bit skew, push them all the way down.
Now for the special trick: ACF-50 the whole caliper, don't be shy spray it and then wipe it with a cloth so it goes everywhere. You want coverage, not excess, do a good job of it, wipe the inside of the pistons. Use the cloth to wipe all those pins and bolts you neatly cleaned with the wire brush earlier on. Grease all the rubbers and shafts that slide in them, use proper rubber grease, put it all back together and wipe off any excess grease (make sure it all moves well.) Now go wash your hands, you are touching brake pads next and you don't want any grease or ACF-50 on the pads. Put a thin layer of copper grease on the back of the pad that touches the pistons, just a film to cover it, nothing excessive. Then put the pads in and fit the caliper back to the bike.
Next time you take the callipers off you'll be amazed at how easy it is to clean even if it looks like crap, will take you half the time. My rear brake used to be the worst until I tried to ACF-50 it. Twice after that I took it off, used a tooth brush to clean the bit of the piston that stuck out and pushed it back in by hand because it was still working well even though the caliper was really dirty. Checked that the sliding pins still worked and put it back on without cleaning anything. That's 2 cleans I didn't have to do because it was done properly and ACF-50 coated before.
I have 2 sets of spare stock callipers now that I have changed to CBR600 brake callipers. They got this treatment too, wrapped in newspaper and stuck in ziplock bags for storage. I'm sure they will look as good as new when I take them out of the bags even if they are in there for a few years.
