Originally posted by Dipsoid Electronic parts are actually more dependable than mechanical parts. Look at the issue Pentax had with the aperture actuators on the K-xx series. Yes, there is one other thing that can fail, but one less mechanical thing that can fail. Personally, I prefer a mechanical aperture, because a mechanical failure can be fixed fairly easily, parts not in production can be 3d printed or had from a doner lens where as good luck fixing the circuitry in a fully electronic lens. Plus, a fully electronic mount makes macro a pain, there has got to be nothing as annoying as using a canon lens with a dumb extension tube, and ones that communicate with the lens are stupid expensive.
Some electronic component are extremely durable, some other are not. It really depend. A chip like a processor can last a very long time and is very unlikely to fail. What fail typically in electronics as an example are power capacitors, in particular if you don't spend enough money on them. But it also seems that lot of mechanical things controlled by electronics are prone to failure too.
In the end that always a mater of price and design. Getting a car, even mostly mechanical to still be in good shape after 1000 000 kms is almost impossible. But for trucks it is common.
I don't think this is linked so much to mechanical or electronics part than fitting the design/specifications. We know clearly that a K30/K50 life expectency isn't the same as K5 or K3. Like we know that SDM of 16-50 is to be avoided while lenses like 18-135 look to work flowlessly.
Sure as the PLM motor for Pentax is new and KAF4 is new too, there more risk of an unknow design issue but the first problem is likely that it is not built to the same standard as a DFA70-200 rather than the technology used.