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This is more for keeping her running well but I suggest changing the spark plugs every alternate oil change. My oil gets changed every 10k miles and plugs every 20k miles.
It sounds to me as if you are doing the right thing
If I think of anything else I'll post.
Judging by the gunk that my catch tank collects and also comment from JKM who inspected my valves and they were cleaner than expected, I can't say conclusively that a catch tank system is essential but I have the peace of mind that it helps.
For anyone who doesn't know already, I've driven over 100,000 miles and still going strong - Look out for that 75yo old GIT who drives an old Mk5 GTI, it will have done 200,000 miles.