Best Way To Maximize Preamp Tube Life?


I would love to learn how to best maximize tube life. Tubes have a limited lifespan, of course. So when you're not listening for a time, is it best to shut everything off to preserve the "hours" left on the tube's life? OR does the act of powering off/on itself shorten tube length as well? If so, by how much? Something like "powering off/on costs 3 hrs of tube life, so taking a music break of less than 3 hours, better to just leave it powered on." Or 1 hr, or 10 minutes, 6 hours, etc? Where is the tradeoff point?

In my system FYI, I am running a Don Sachs preamp with 4 6SN7s and 1 6BY5 rectifier.  Don says the preamp is only running the tubes at 40% of their rating. I would greatly appreciate some input from people with tube knowledge. Thanks in advance!
sid-hoff-frenchman
You can take the advice of the designer/manufacturer or you can take the advice of a random guy on an audiophile forum.  I say leave it on 24/7 and replace the tubes every 12 to 18 months.  This assumes you listen more than four to six hours daily and that the sessions are not continuous.
Turning a tube system on 2 or 3 times a day doesn't hurt it all.
@donsachs 
That sounds about right. Thanks for joining the conversation, Don.



My amps turn themselves off after 30 minutes being idle. So I never tune them off manually. Sometimes I come back to listen within 30 minutes, sometimes I don’t. 
Tubes are NOT like fine wine! They DO NOT improve with age! If fact when they are brand new and at 100% cathode emissions that is their peak performance. They only decline with use as the cathode coating gets used up. James Bongiorno pointed this out years ago when he worked at SAE and was asked why he doesn't design with tubes.