Can you do anything to make power tubes last longer ?

Yes, the concern over skin oil has to do with light bulbs, not tubes.  The oil deposited on a high intensity, high temperature light bulb will carbonize from the heat.  That leaves a black spot on the bulb.  The light from the bulb is absorbed by the black spot instead of passing through and that makes the black spot MUCH hotter than the surrounding part of the bulb causing that spot to fail.

Another piece of advice is to grip tubes which have a base by the base and don't push and pull on the glass envelope.  The concern is accidentally separating the base from the glass envelope.  

Also, if you do a lot of tube rolling, be aware that tube sockets have a limited life in terms of how many insertions and removals before the connection becomes less reliable.  An old time technician told me it can be as little as 30 insertions and removals for a socket to fail (i.e., cannot be re-tightened reliably).  If you do a lot of trials, consider using socket savers while you are trying to find the right tubes.

Alright, I will join you in the abandoning the ritual of using white gloves while handling tubes. And the grip is indeed worse than bare hands.

Having extra set of all needed tubes is of course always a good idea, well, some tubes are really expensive and hard to find, at least from reputable sources.

I am not going to use any new reissues, only interested in vintage tubes. I see no reason to just waist money on inferior sounding and less reliable tubes. But if you need 20 power tubes, yeah, you just might be forced into that. I only need a quad.

Paper towels ftw

I am not going to use any new reissues, only interested in vintage tubes. I see no reason to just waist money on inferior sounding and less reliable tubes. But if you need 20 power tubes, yeah, you just might be forced into that. I only need a quad.

For bigger KT tubes, it’s extremely hard to find good vintage ones anymore. There are still some late make GE 6550s out there. EL34 (like your amp uses) and 6L6GC is much more feasible for sure. The British Mullards are warm (like your SED / Winged C, but better); I preferred Amperex / Holland EL34 for being more a bit more neutral while still sweet sounding. The East German RFT / Siemens are supposed to be quite good too. Electro Harmonix EL34 is a copy of this tube, at least superficially - but the old RFT build quality was much better (straight glass bottles, even!).

I’m quite fond of many of the Russian power tubes so it feels wrong to call the "inferior". But yes, the old power tubes were generally better. The old EL34 were beautifully built.

Also remember - part of VAC’s "secret sauce" is Kevin’s voicing expertise / craft, and it’s usually advisable to stick with tubes that sound at least similar to what it shipped with. What does VAC recommend for an Avatar these days? They were shipping Shuguang KT88 power tubes in 2000s (some with Penta Labs labeling), but Shuguang is long gone. I have a VAC 450S that originally shipped with those Shuguang KT88. They wore out before I got they got. Russian Gold Lion KT88 didn’t sound good in it, but fortunately Tung-Sol KT120 do :) Now that I think of it, might be worth tracking down some Shuguang KT88, sometime.

It would certainly be interesting to try vintage Amperex EL34 but I am currently on the hunt for Mullards XF2 and getting close to them. XF1 would be much more expensive and even more difficult to find. Then there are first generation Mullard EL34 with metal base that some people consider the best. Well, probably impossible to find a matched quad or at least pairs in excellent condition, so I'll just forget about it. Unless I get very lucky.

Yeah, probably "inferior" was a wrong word not always accurately reflecting the difference.

Of course, SED Svetlana Winged are a copy of Mullard, sound signature should be similar.