From conrad johnson's web-site........
"To obtain maximum tube life, vacuum-tube products should be switched off when not in use. A good general rule for is that if you will not be listening for more than an hour, turn any tube component off. Conrad-Johnson solid-state preamps (including Sonographe and Motif), on the other hand, are designed to be left on at all times. We recommend switching power amps off when unattended and over night."
How long do tubes last?
A. That varies depending on the type of tube, the number of hours of use and the type of use they have had. Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time.
"To obtain maximum tube life, vacuum-tube products should be switched off when not in use. A good general rule for is that if you will not be listening for more than an hour, turn any tube component off. Conrad-Johnson solid-state preamps (including Sonographe and Motif), on the other hand, are designed to be left on at all times. We recommend switching power amps off when unattended and over night."
How long do tubes last?
A. That varies depending on the type of tube, the number of hours of use and the type of use they have had. Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time.