I had my SNES running for 5-6 days while I romped through Super Ghouls 'n' Ghosts the first time when I was a kid. Still have that very SNES. No moving parts = WIN!
I was once the owner of a local video game shop. I had a display NES That was on 12 hours a day, 6 days a week. I occasionally forgot to turn it off. I owned and ran the shop for 5 years and it never broke. I know the owner whom I sold my shop to has since replaced it. However, it worked for me a very long time.