Consider that most failures, tube or solid state, occur when turned on. This is do to the physical distortion inside the devices as they heat up. In both cases it is due to thermal expansion and contraction in the material that are heated. I remember the story of the oldest working light bulb being back stage in theater on Broadway in New York, it was only off when the city power failed so there were very few turn-on.
This would suggest that a slow power up would extent the of the devices. Perhaps simply putting a light bulb in series with the power line with a bypass switch for on, the bulb would restrict the current to the unit keeping warm but not hot until wanted to use it.
It is more complex than that but this should start your thinking
