while i respect the theoretical considerations, i don't think it can all be dismissed as "psychological." the theoretical world and the mojo world are two different things.
try this: next time you play a three-set gig, put your amp on standby during first break and try to observe how long it takes for the amp to "come back to life" when you start second set. then on second break, leave it on full power before you start third set. see if you notice a difference. i do. hot tubes just sound better!
