Can you do anything to make power tubes last longer ?

Good tube equipment will last for decades with only occasional tube replacements. The only problem, two problems in fact, NOS tubes will be getting more expensive and more difficult to find. But some transistor equipment is also very reliable, think Gryphon and Accuphase, as an example. If not tubes - that's what I would have.

It is VAC Avatar SE integrated.

Good tube equipment will last for decades with only occasional tube replacements.

Hmmm . . . decades?  I don't think you will get decades out of output tubes unless you skip using your amp for a decade or so.

Of course, not, just replace tubes as needed.