If your down to a mass of bits on the bench then swap them while your there. They should be good for anothor 15 years yet but the replacements should be cool for another 30. I'm thinking along the lined of corrosion on them. They are peanuts to buy, a chisel through the middle to remove and the new ones just tap in... any cleaning within is then as far as you want to go with it.
Imagine trying to get to the most inaccessable ones in the 101 once it's fitted and it'll make the extra work worthwhile.
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