Work does expand to fill time available. And customers are being asked to expect that Apple's components will last 3-4 years. But isn't that reasonable to expect? When you buy a car, do you expect to have to replace the cylinder heads in a year or two so that you can gain the 15hp that BMW will add to next year's version of your M3? No, most M3 buyers -- despite the performance nature of the model -- are more than happy to live with the car as-is the moment they take delivery. (Second owners tend to do more mods.)

Studies also show that most failures in modern equipment tend to happen within the first year or after the fourth (when the machine becomes so slow -- due to bloated software upgrades -- that it churns and churns, generating loads of heat that then "fries" components). Year one is covered by warranty. And after 3-4 years, the machine is due for replacement anyway. And there's always extended warranty coverage (AppleCare).
So, I'm not arguing the validity of your points -- they're all very accurate. But my question would be: So what? Few people fix their PCs. Most just replace them once they're out of warranty. In that case, what's it matter whether the "dead" machine is loaded with standard or proprietary parts? It doesn't. Except maybe for the second owner ... and Apple sure isn't concerned about them (nor is Dell, Asus, Acer, Lenovo or any other PC maker -- they all want to sell new machines to users every couple years).