I dont like to think that I'm ruinning them in any way!
If you have that thought in the back of your mind then you probably won't go wrong.

I am far from an expert, but if you have a tool that is so run down that you can't use it, then you have to think about whether it should be used (and tools were meant to be used) or if it should be preserved/conserved from further damage and 'kept in a time capsule' as such.

I am in the 'tools are for using' side of things, and I think that you have done a damn good job of keeping it "alive".
Well done.

Today I came across an artist that is using a cast iron printing press made in the 1880's press for printing his art, bearings and rollers have been replaced and its been repainted... but he uses it for all his printings. And he smiled when talking about using such an old, useful, tool.