Mine are over 25yrs old now and still in perfect working order. I change brake/clutch fluid each spring, and find they clean best in plain soap and water. Then a quick spray dry with compressed air. Any remaining residue, which can accumulate on the sealing edges, is then easily removed with a slight rubbing of a fingernail.
Curious.........what has happened to yours, that they need replaced, 21Turner? Are they physically torn? Weather checked? Maybe a bad accumulation of scaly oxidization around the edges? Just curious.