I just bought the last pair of NOS Mullard M8080 tubes from CJ. My CJ Classic preamp requires 2 each.
This tube has been out of production for more than 45 years now.
According to CJ other M8080 tubes out in the market place are noisy and not suitable for my preamp. I stocked up early on and now have 7 pairs of backup tubes. These tubes usually last a little less than 2000 hours. I currently have about 300 hours on my current set of tubes. I should have enough backup tubes to last me the rest of my life.