#1
Does it wear out your tubes to leave the amp sitting on standby for long periods of time? I know I'm going to have to replace tubes eventually from playing, just wondering if I should be more conscientious about completely powering the amp off between practice sessions. Is it worse for the tubes to be power cycling them off and on, or to leave them on standby for an hour or two while I do other things?

I have a Mesa Boogie 5:50 Express, if that matters to the analysis.
Fender American Deluxe Stratocaster
Epiphone Sheraton II, Seymour Duncan Jazz and '59.
ESP Horizon NT II
Epiphone Les Paul Custom
Mesa 5:50 Express
Egnator Rebel 30
Hughes and Kettner Tubemeister 18
#2
You should not leave your amp in standby anywhere close to an hour. Just turn it off man then turn it back on when you return.
Ibanez SIR27
Pod HD500x

RIP:
Mesa Boogie Roadster 2x12 combo
Cmatmods analog chorus, phaser, tremoglo, signa drive, butah, and deeelay
walrus Audio Descent