Not to hijack the thread.... I am making a product used by the FAA (Federal Aviation Administration), where "new" equipment is from the 70s. I don't know if my device will ever see widespread adoption due to inertia in the organization, but it did pass a year old evaluation with flying colors (sorry, couldn't resist) and when somebody suggested the devices had to come out of the control towers, I think the guy feared for his life when the Air Traffic Controllers heard his plan.
My design premise has been that this must be absolutely reliable (zero failures of any kind at the 10 test locations in the year evaluation year suggest a good start on that) and it must be serviceable for many years into the future. The $$$ industrial switches are rated for over a million cycles; by my calculations, that's at least 15 years in the worst case. But switches can fail early, so I have made sure that they are field replaceable with no special tools required. The displays are 15mm 7-segment LEDs. If they last for 50,000 operational hours, worst-case, that's pushing nearly 20 years of operational life. Sorry, replacing these will require soldering but I am fairly confident that replacements would be available if somebody wants to keep them running. The microcontroller is a PIC18F-seriea without any exotic features, so I'm not concerned about availability of that part either.
While my FAA contact appreciates all this, sometimes he just doesn't seem to get it (that can be said a lot when dealing with the FAA). "Why don't you just use a raspberry pi and some of the cheap oLED displays? Or maybe an LCD touchscreen?" I don't think anybody would predict the operating life of a cheap oLED display in operation all day every day. And finding a drop-in replacement in a few years or 10 or 15 is really unlikely. The same with an LCD touchscreen display - if there's a mechanically-interchangeable one to be found, it's likely that minor or major software changes would be required.
Sorry, blowing off a little steam, but that's been my thought process for something that may well be in use long after I'm around.