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