I've been a NIB buyer for 5 years.
To date, sometimes things need to be tweaked/replaced during a new games "break in" period. The manufacturer has always sent me the part and I put it in. Almost all my new games needed something.
After that, I've had switches need to be tweaked or replaced, and on some of my oldest games I've done flipper replacements (rebuilds) when they start to act up. I've never had a game go "dark" for extended period of time.
That's all games in a HUO environment.