I'm not so sure that physical vs mental makes long hours any better. There are many days I go home with a ringing head and blurry eyes because I've been staring at a screen for hours and in meetings with people who all want a different outcome (thus no solution is acceptable to all).
One of my first jobs was very physical, and although I went home with tired arms and back and sore hands, there was something numbing about that which I found pleasant.
I think the difference between long hours depends on how hard you're working -- whether physical or mental -- vs those who just get by, whose days come easily to them because they are not challenged or do not challenge themselves.