when's the last time you popped out the piston and cleaned behind that seal that sits in a groove in the cylinder wall? (this is the caliper piston i'm talking about). i replaced my seal when i did it, and they're cheap, but the one i found in there was still rather flexy. clean gently with toothpick or other stiff-but-soft implement.
as to whether this step will prevent the symptom next season, it probably depends on a lot of environmental factors.
also cuts down on the "peep peep peep" syndrome, as endearing as that is.
jc