Service the coin unit and player unit steppers once a year. At minimum remove the rotors, remove the year-old lubrication from the disks, along with the accumulated dirt. Clean the shoes and brass rivets till they shine and then re-apply a very thin layer of white lithium grease. Put a drop of 3-n-1 oil or teflon oil on the metal to metal stepper pivots. Good till' next year.
Also do the other steppers while you're at it.
Another thing to consider-
Suppose you are going to play solo on a 4 player game and you know you're going to be there for a while enjoying it. Don't (always) choose a 1 player game. Choose a 4 player game. That way the steppers stay active across their entire range and the wear load is spread across all 16 score reels not just 4.
Just because it's a multi-player game doesn't mean it shouldn't be reliable.