Just curious if it hurts preamp tubes to leave tubes on for like 24+hours? I'm asking this with regard to a Project tube box s2 phono preamp. Twice now I have forgotten to turn off the preamp and left the tubes hot for 24 hours. No music was playing but the unit was powered on and generating alot of heat(as it does) I'm not sure why they didn't include some sort of auto off feature or at least a standby mode like tube driven guitar amps. Anyways, did I ruin them or damage them? From now on I will put some kind of reminder for me to remember to switch it off but do I need to order new tubes?