Never heard of Sealmate and fork oil is not something I change on a regular basis. I figure it is a sealed system so outside contaminants should not be an issue. However, I am serious about cleaning the fork tubes to keep them free of anything that could damage the seals. I think a 10 year interval between seal replacement is a good span, one that a lot of riders never see because they sell their bikes well before they have had them for that long.
You would be amazed. I've pulled many forks apart and they are ALWAYS filled with a silver tinted brown soup. Even when a fork seal goes early and you pop it apart thinking this won't be too bad I did this not lone ago, yet it is.
What usually wears out are the bushings and that is usually due to mileage and or contaminated fluid. There is a grey coating in them that disappears and then it starts chewing up the copper bushing itself. The seals tend to last much longer unless a dust or sand particle wedges itself in there and create an escape route for the oil.
I forgot about that. I still have some 35mm negatives somewhere.I remember when 35mm camera film was the go-to MacGyver "tool" for fishing out crud from fork seals, but good luck finding that anymore
