Funny you should mention 6922’s. My phono preamp uses (2) also. In 02/2018
I ordered (2) NOS Telefunken E88CC/6922 - Platinum Grade - Cryoed for $217 each from Kevin Deal of UpScale Audio.
He ha a video of the Tele’s saying they would last from about 5,000 to10,000 hours: https://www.youtube.com/watch?v=-g2VhyU69Og
I haven’t had any problems with them at all. When it comes to tubes, I’ve learned I will only by from UpScale Audio or Brent Jessee. It’s a shame now cause the price of those tubes are almost unobtainable now.
Brent Jessee even has a return policy on his tubes, which is almost unheard of. Buy tubes only from someone you trust, has a return or at least a replacement policy, period. As UpScale Audio has.