C-17
The original specification from McDonnell Douglas defined a service life of 30,000 hours. Since it came from the home of the DC-10, one can expect that it will soldier on for upwards of 100,000 hrs without major structural upgrades as most of its flying is long haul.
Re painting over white-walls, I haven't seen a vehicle so equipped for years except on restored 1950s vintage cars.
Boeing's intention of building "white tails" reminds me of a couple of British firms that developed aircraft as private venture and subsequently helped save the Nation.