Can you do anything to make power tubes last longer ?

Right. I wouldn't like to end up with too many tubes.

Yeah, people chase vintage tubes usually for a good reason.

XF3/XF4 as a spare set..that's not a bad idea at all.

Reducing heat by venting the component or cabinet can extend tube longevity. Suggest that you visit; https://acifinity.com

for a wide selection of component/enclosure heat extraction units. I have one of their units placed directly on top of a Prima Luna EVO 400 integrated amp.  It's like they are made for each other.  It drops the temp around the tubes by about 12/15 degrees.  Btw since these are extraction units rather blowing cool air onto the tubes there is never a risk of thermal shock damage to the hot tube.

Enjoy the music..

Here’s a little tube porn for ya:

Tube porn, right.

@tomic601’s mention of Roger Modjeski leads me to suggest that for longest tube life, they can be installed in any of Roger’s Music Reference amps (RM-9, RM-10, RM-200), in which output tubes last about 10,000 hours. Compare that with ARC amps.