Quoted from Benepinballs:After playing all my modern Sterns, All the bally williams seem cheap and feel cheap. Most of the operators I know have had fall less service problems with Sterns, bally williams were always having problems on location.
Well now you know one who has had tons of problems with Sterns! I will happily admit that they do get played the most of my games on location, so that definitely plays a role, but they have far more serious and frequent issues than my B/W games. Most of the time when one of the B/W games has a problem it ends up being something really basic like a broken wire. The Sterns tend to have dead transistors and optos, and shattered paper-thin ramps and plastics. Oh, and almost every single EOS actuator has snapped off. I just begrudgingly ordered $150 worth of the pieces of junk yesterday. I know people claim Sterns don't need EOS switches at all, but my Iron Man's coil burned up days after one of the actuators snapped off, so I figured I'd play it safe and replace them all.
When I put my Iron Man out less than a year ago it was new. The other day I found the entire right side of the right ramp snapped off, despite the ridiculously flimsy included metal "ramp protector" (I should've gone for the Cliffy). Sure, B/W games have ramps that eventually break too, but this wasn't just a crack or small chunk. We're talking about a 4 inch length of the wall of the ramp, all the way up to the screw. The plastic they use these days is just pathetically thin.
To answer the original question though, there isn't a point past which Sterns started looking and feeling cheap, however you define that. They have always felt this way. Search RGP, you will find posts about the cheap feel dating back to Monopoly and certainly back into the Sega/DE years as well.