Turning tubes on and off helps the tubes last longer.
I believe this is particularly true at turn on when you do what I used to do with my tube amps.
That is, I bring the heaters (filaments) on first, so the plates and everything warms up, then with a delay circuit after 1 min I switch the high tension on.
The reason was because NOS RCA Black Plate 805 tubes were very expensive if you could find them.
And of course tubes don’t age when they’re off, wolf was just having a dig!
Cheers George