Can you do anything to make power tubes last longer ?

Sure, that’s a fine strategy - stick to seeking what you really want. But I’ll say that even XF3 and XF4 Mullards were much much better than SEDs, to me. I didn’t really like SEDs; they came off as a 1-trick pony for lots of warmth, lacking the articulation and 3D holography of British Mullards. That seems to be a common pattern with modern tubes, or Solid State components that try too hard to emulate the vintage "warmth".

You could get some nice XF3 / 4 to use in the meantime, and then they become great spares when you get those XF2’s :) This is how I ended up with tons of tubes lol...

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.