Can you do anything to make power tubes last longer ?

I make my tubes last longer by turning my second system on.  I'm fortunate to have a solid state system that I use 75 % of the time.   I have always been told turning amps on for short periods then off is bad for tubes. 

I do bias right at or a little shy of amp mfg specs.   I don't think it's good to under bias either so if it says 53 ma that's where I usually put it.  I use this

https://www.vhtamp.com/avtttt2

Great way to know where you are at.   

For me my best bet is to buy matched quads or pairs depending on application from a trusted seller.   I seem to have much better luck and durability 

Some tubes just last long , some don't.   I have a quad of Gold Lion KT88 that I keep as a spare.  They have a ridiculous amount of hours.   They look nasty, getter is fading , silkscreen is gone.   They test strong still, not far from min new and still sound good.    

On the other hand I had a quad of new Mullard el34.   Did not have then matched / tested and within a month I had one burn up.   

So to answer the question, not much you can do but enjoy and not leave em powered up when you're not listening  

Check the heater voltages. If they are above spec, the tubes will fade a lot quicker. Most of the time this is due to high wall voltage above 120V (or 240V) so you can't do much about that other than a transformer. If the wall power is okay then the amp should be serviced. Anything above 6.3 or 12.6 volts on the heaters is either careless designing or fading components. You don't want to stick expensive NOS tubes under those conditions.

  I have always been told turning amps on for short periods then off is bad for tubes. 

I would think that repetition would be the key to avoid on this one.  

gs5556, how do I check heater voltages ?

oddiofyl, I could have a second system too with my old SS amp but I just wouldn't listen to it !

Those new EL34 Mullards, are they new reissues or vintage ?

Balanced power supply. It provides exactly 120 volts at exactly 60 Hz...constantly.

IMO critically important to provide to tube amps...well, if you want your tube amp(s) to sound as it/they were designed to sound, which, sanity indicates you should. Oh, and bias holds better which increases tube performance and longevity,...huh, so I guess the more accurate sound is just a bonus to the longer tube life...funny how that works...