Can you do anything to make power tubes last longer ?

It's been a while since I ran amps that required biasing, but my approach was to start at the low end of the builder's recommended range.  Then, in part because I'm lazy and because I want to be gentle on the tube.  I would just leave things be and not bother to check the bias.  As the tube ages, the current flow drops on its own so the bias point drops.  By not changing the bias to compensate for the drop, i am actually preserving the tube, albeit with a small loss in output power.  

Put the Mullards XF2 in. Great tubes, probably need a little of burn in time. So much better than SEDs. Hold the bias perfectly. Should’ve bought them when I bought the amp. Noble, balanced sound.

When I don’t listen to music, all power off.

Power on, standby, etc...., I don’t do that.

When I want music, I just all power on. After 5 minutes, almost full performance comes out.

24-hour-on mode does not give much better performance than 5-minute-wait mode.

If you doubt it, just do the both ways. You will realize my opinion is CORRECT!

I'd say, in the case of my VAC it is 10 minutes of warm up minimum, I usually do a little more than that for critical listening. And VAC's manual says the same - 10 minutes before tubes warm up fully, especially if you want to check the bias before you go.

This is a situational maybe.  In South Florida especially during hot weather in densely populated areas we experience fairly large voltage fluctuations.  During peak demand hours at my location voltage can range from ~105-120 VAC.  Power tubes were constantly needing to have bias adjusted.  Like weekly.  I bought a power regenerator, originally a PS Audio P10 later a P20.  Tube bias requirements dropped almost to nothing, like once every 6 month I check but almost never need to adjust, and tube life at least doubled.  So if you live in an area with high peak power demands and consequent voltage fluctuations taking steps to regulate your power supply could extend power tube life.