That's all good to know. In '17 I powered up a tube amp of mine that had been dormant for nearly ten years and in '20 I powered up another tube amp I owned that had been in hibernation for well over ten years and i wasn't aware of this stuff so I basically plugged them in and turned them on.
I guess I was lucky.
That second amp I alluded to has been asleep again for about four years so I guess I should look for a variac on ebay. The second amp, the one that woke up in '20 and then went to sleep again, does use a tube rectifier though.