I have a stash of 1950's blackplate RCA 12AX7's and 6V6's, and a stash of early 60's Mullard ECC83's (12AX7's) and I use them nearly every day in my amps, just as the God of Amplification intended. I carry a set of EH 6V6's in my Super Champ as spares, to be used only in a case of absolute emergency. For my EL34 amps, I have settled with SED Svetlana's, because Mullards are just too hard to find and afford. I started hunting and gathering in 2003, and have what I hope to be a lifetime's supply. The only moment which exists is now, so that's when I want excellent tubes in my amps.
Cheers......................wahwah