I know for one thing there are at least 1000 VDC/Electrohome PJ out there in simulators. Two companies in Florida service at least half of those and they are run mostly 24/7,thats over 8500 hours in a year. One service person I know says their contract is to replace the tubes between 5000-6000 hours. so the demand is still there and they wont go down any time soon. i think there are three companies that still make the tubes, with VDC and Thomas being the Largest.
Athanasios
Athanasios