If you can feel them as raised and hear the ball moving over them its wearing them down a tiny bit each time. It could take several thousand plays to cause serious damage or maybe less. I would at least consider something like mylar, but only if I was sure I could later remove it without causing more damage than would otherwise occur if I played it as is until I could strip playfield and permenantly fix.
I leave this stuff alone and play my games unless its bad and getting worse. Then a band-aid until a permanent fix is reasonable and prudent.
If its some pristine example thats special and perfect or has special meaning to you- then you probably need to stop playing it and fix it.
Deer Park, NY
