The LX does seem a bit more highly strung than the other Pentax MF bodies. I get the impression that unless the one you're about to buy comes with a receipt to prove a recent CLA from a reputable workshop then you need to budget for that treatment in the near future.
Meanwhile the only thing which seems to be able to kill a K series is serious mistreatment, such as dropping from a great height or drowning.
I forgot to mention earlier that the original three K series can all handle film up to 6400 ASA (3200 on the K1000), for some reason the MX was limited to 1600. Again, very odd given that Pentax obviously had the electronics to handle a wider ASA range but just chose not to fit them to the newer model. I would wonder if they decided to limit it as there wasn't much film of that speed rating available at the time - "The Asahi Pentax Way" which came out around then regards 200 ASA as blisteringly fast, and the idea that people might be still using the cameras over thirty years on with faster films probably didn't play a huge part in the design process!