You guys should start reporting/logging flipper issues based on flips. If i remember right, audits show how many times each flipper has been flipped? That would be a more accurate lifespan of the coil stops etc, as flips vary greatly from game to game. Also some games typically get more play on one specific flipper.
Good info in this thread though, ive seen both the button pop off and coil stop issues with location sterns here and a friends personal machine. Planning on getting some new sterns myself soon, so ill grab some extra supplies and be prepared.