When should the pencil tip be replaced?

This is what Apple says here https://support.apple.com/en-us/HT205236

Under the Title "Replace the Tip":

"If the tip of your Apple Pencil becomes worn or damaged, you can replace it. There's an extra tip in the box, and you can buy more if you need to. Just unscrew the tip and screw in the new one."

I have been using mine daily for over a year for writing as opposed to painting and it’s fine. There was one point when the letters became like dotted lines but I cleaned the iPad and it was fine again - greasy screen rather than the pencil tip so before going to expense of changing tip, give your screen a clean