lifespan transmitter driver amplifiers

[old_tv_nut]

Tube outputs are still in use.
Maybe someone with direct experience can comment on reliability.
Early stations did not stay on 24 hours a day.
Some stations install dual transmitters, so one can be off air if necessary, with a temporary 3 dB reduction in power.
High power solid state transmitters can be designed as many lower power modules, so failure of one or two is hardly noticeable.