My drives have been on for two years, with a couple of short power offs when adding new computers, gear, etc.
Everything stays on all the time. I don't own any tube gear through right now, when I do use tube gear, it goes off.
When Digidesign had a problem with power supplies on their Control 24s, mine was one of the recalled units. But since I had it on for about a year, I never had a problem.
I turned it off one day, turned it back on, and got a horrendous buzz. "You probably didn't have any trouble because it was on all the time," said the tech at Digi.
PS....when is the last time you saw a light bulb go out unless you were turning it on?