Can you do anything to make power tubes last longer ?

marco1, thank you.

Yes, so now I have 12AX7 Mullard long plates in the preamp, 12AU7 RCA black plates in the driver and Mullard EL34 XF2 power tubes. This is done. Now I will have to think/experiment what to put in the phono stage, since I don't care much for the Brimars that are currently there.

The price was reasonable. A little more than new SED tubes cost.

I’ve always liked the RCA 12au7 black plates. I remember discussing them on another thread with you and Mulveling. I’m currently using RCA 5816A black plates as a driver in one of my amps. They’re a little more refined and warmer than the 12au7 and although I’ve never used them in combination with Mullards EL34 I think they would compliment the Mullards nicely.  Something else to spend your money on if/when you get the itch 🤑

"Next year maybe, I spent enough already. I would be cautious to take the sound in  warmer direction compared to how it is now” yeah, next year you will be one year older, and hopefully everything around you will be “warmer” LOL

@inna 

That was one of the reasons I went with Hybrid stuff. I currently have PS Audio.  The BHK preamp that uses two 12AU7’s and the mono blocks are currently using 6922’s.  All of which can be affordable and last a fairly long time.
My downstairs mono blocks use 4, 6HB5’s in each and they starting to get expensive to replace. I’m still using an ARC SP9 MKll Hybrid preamp with them and it uses 6922’s also.