At least in aerospace, the 2,000 hr spec comes up often as a reasonable service life. We could make everything last forever, but that usually means beefier, heavier parts. How much more in fuel per flight hour are you willing to pay for a product that lasts longer? What about decreased range? Also, how much of a unit cost increase will you accept to pay for larger chunks of aerospace aluminum? Tradeoffs are necessarily driven by consumer demands.