I have been impressed with the fact that one can pull and switch tubes from the Atma-shpere’s while they’re running. Of course some highly insulated “grilling gloves are necessary, unless fried fingers are on the menu that day.
I also asked Ralph Karsten a similar question about switching speaker cables and interconnects and whether it was prudent to do so with the amps in standby. Ralph said standby was fine. But he then advised that he usually didn’t bother with standby and just left the amp on, saying it was “pretty good that way”.