Can you do anything to make power tubes last longer ?

And fewer on/off cycles, I suppose ?

I think that there may be differing opinions on that, @inna . Personally, I do not like to leave output tubes idling when I am not around/in the close by vicinity. The older I get the more neurotic I get.

But the way I listen these days in only once or twice a day . . . it’s ot like I am in and out and turning music on & off. I will say, however, that even back in those days I never left tubes on when I was out of the house.

But: the sort of exception was with my first tube amp before I knew anything at all of what I was doing. It was (and I still own it) a Cary SLA 70 signature and it has a standby switch. With the standby switch in ’on’ the tube filaments are constantly being heated. I’d have to get into the manual to tell you exactly which filaments are heated and glowing, as tubes and electricity is not second nature to me. Anyway, as I was learning the hard way basic stuff that every tube owner should know, I was talking to the service rep guy from Cary (this is back in the ’90s when they had great customer service) and he said it was not his advice to always leave the amp in stand by as I had been doing. Therefore, I then started using the standby switch in sort of a sequence . . . in other words first go to standby for a while before I went to ’ON.’

As far as preamp tubes, I don’t leave my pre on when I am not listening, either, but there have been threads on that subject, and I know that there are some that do.

I use a variable speed cabinet fan at the lowest speed to pull heat out of my ARC preamp. Can't hear it and it certainly does not hurt. Of course, no data to say the tube life is being extended.

But, I only use the system an hour here and there during the week. 

Oh no, I never leave it on when I am not in the house, or overnight, for that matter.

Though my VAC has some circuit that shuts it down if power tube runs away.

I suspect you already had it. Don't leave on and less cycles. My  understanding is that tubes become less reliable... as in more likely to blow as well as have the sound quality slowly deteriorate. This is enough for me to change at recommended intervals. Three thousand hours takes a while even at the 2 - 3 hours a day, which I use mine. 

I wouldn't replace expensive and hard to get tubes unless they do something audibly/visibly wrong. But if you use new productions tubes, yeah, why not ?