OTOH, I upgraded my parents' PC yesterday, after three months of downtime. It really took at least two hours and four reboots. The machine was screaming and the task manager showed a blue rectangle for CPU load (uninterrupted 100%) and a green one for the disk load (again, uninterrupted 100%) while nothing was usable all the time.
Same process takes <10m in Linux (specifically Debian), and an optional reboot, without any hardware load drama.