Mine are all vintage/restored, so I plan on keeping them. I have been buying NOS tubes as backups. Interesting article but right now I’m looking for the “old stuff” 1960s and 70 RCAs, telefunkens, Amprex, etc. and it’s like “get it if you can.” I would be also be interested in listening to the new tubes from Western Electric, also I’ve heard of new solid state power tubes from Soundsmith as well.
Don't sell your tube amps
Although this was an article in a guitar Magazine, I thought it might interest those who own stereo tube equipment:
https://www.premierguitar.com/gear/amps/dont-sell-your-tube-amps