When I worked at Microsoft, Windows took far, far longer than an hour to build from scratch. I remember walking a few buildings over to the burn lab to pick up DVDs of the latest build. I don’t have any hard data, but running a full build on your dev box was very rarely done.
The dynamics of commercial projects can be very different from open-source. You're much more likely to tolerate sitting through long builds if you're being paid to do so.
Like, for example?