Question about valves running hours


I'm new to the tubes world and when I bought my amplifier the seller told me not to run it for more than 8 hours, letting it for rest a couple hours before the next listening session. I wasn't told why, but now I got curious and I want to know more about it. 
What's the reason for this limitation? What can we damage and why?
128x128migueca

Showing 1 response by tablejockey

Doesn't  anyone remember?Vacuum tubes powered WWII.
Doubtful equipment was on a timer and shut off after 8 hours.

That being said, it doesn't mean keep it always on, just turn it off when you're finished listening. It is a good idea to at least have the amp in an open rack  or top shelf for ventilation.