I think I've only had one bad switch on any gun I've ever owned(old timmy) and I broke that one due to my own stupidity. I don't remember exactly but most of those switches are rated in the millions of clicks so you're pretty safe. There's always the possibility one can get a dud I suppose. Or if you were to let it rust there could be problems. Other than that, it's pretty much a non issue.
Old school angel poppets/cup seals(LCD and A4/speed), spring detents(not sure which models) F/S