I do not know what the record is for the longest tube life, however, this particular tube lasted 17 years, 11 months, and 23 days. That’s 157,596 hours.
I had written about this almost five years ago: https://www.engineeringradio.us/blog/2014/12/longest-tube-life/
The last one was last fall: https://www.engineeringradio.us/blog/2018/09/i-almost-hate-to-say-anything-but/
This was installed new in a Broadcast Electronics FM20T transmitter which was placed online on June 6, 2001. It lasted until May 28th, 2019 with almost no downtime. Towards the end, the emissions started dropping off and we increased the filament voltage up to 10 volts. When you have to increase the filament voltage, that really is the end for a tube.
The new tube was put in and I carefully marked out the date in the maintenance log. The hour meter on the transmitter stopped working several years ago.
Prior to this, the longest tube life I’d experienced was an EEV 4CX35000C from an MW-50B transmitter RF section. When that tube came out, it looked like it have been on fire.