I have had my TNG since ~2001 with ~6000 plays and relatively few issues. I think the "mode start" opto just burned out (they are bulbs after all) and I had to reattach a flipper wire, and adjust the "neutral zone switch" one time.
I have also done the usual circuit board upgrades and replaced the GI connector, but that is just pretty much standard on games that old.
All in all, not bad for that many years.
It stays in my collection as it IS hard; games are not long, and I have fun. I honestly just try to get Warp Factor 8, and if I get that, I try to get the extra ball and start multiball.
If I played the game "normally" (time out some modes, try to get to final frontier with minimal risk, go for multiball all day every day... ) I may have sold it years ago. But I have fun playing it my way
Price wise, it is a no brainer compared to many other games. The best "hard" WPC game I can think of... the only really hard WPC game I can think of as well...