mean time between failure

[compucat]

I have observed that many 40s and 50s sets had their original picture tubes replaced within about five years. The replacement tubes seemed to last much longer. Also, keeping the brightness and constrast at moderate settings can extend the life of a picture tube. My 1949 Motorola 9VT1 is still going on a picture tube installed in 1954 although I have had to twice blast away a heater to cathode short in the 13 or so years I have had the set in operation.