Tubes are like incandescent lamp bulbs. They wear out in time, and switching them off between auditions helps lengthen their lifespan. One set of tubes will last for let's say, two to three years (daily use) without losing the sparkle in the treble range, and I'm talking about audiophile-quality use here. Their turning on and off causes temperature changes to the internal elements and this is what shortens their life. It's advisable to turn them some time before listening and letting them warm up to music. An ageing tube loses the top end, then the mids and then the bass, in this order.
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?
What's the reason for this limitation? What can we damage and why?