Smaller input tubes can last 6,000-10,000 hours. That’s much longer than the larger output tubes that typically last 3,000 hours.
MULLARD 12au7 longevity
I bought a pair of these from Andy’s Tube Services years ago for my Rogue RP-1. Thought they would have crapped out by now but they still sound good. He told me they would last a long time. Anybody got any reports on how long you have had these units in service?