tube amp - cool down

The owner's manual says to let my Class A tube amp completely cool down before turning back on. This isn't conducive to A/B'ing cables. Will I damage the amp if I turn the amp off - change cables quickly - and turn back on again. Thanks in advance!
Hi Steakster. What tube amp are you using?
Many professionals/manufacturers recommend 5 minutes between off and on and discourage constant recycling. Perhaps your manufacturer knows thier product better than anyone here and knows of a problem. Or, they might be overcautious. Ask them. I've adhered to the 5 minute rule and have had no problem with any tube device.

FWIW, I would not recommend that decisions about cable be made based on short term A/B'ing. That will only show up gross differences. The differences between high quality cable and IC's should be small and discernable only when you have had lengthy sessions with specific reference materiel for comparison. Short A/B comparisons may result in decisions made on particular aspects which are dramatic, but not enduring, such as cables which have a tendency to showcase 'detail', in the short run attractive, which becomes just plain overly etched/bright in the long run.
Hi Ecclectique. I have CR Developments Artemis monoblocks.
I'm with Newbee. Short term back & forth could drive one crazy.
Does anyone know why the amp should fully cool down? Does it have something to do with discharging capacitors?

I would think that full cooldown is undesirable. If a tube is still warm when it is refired, the thermal stress to the tube filament would be reduced. Also, the warmer the filament, the greater the resistance, which would also slow the in-rush current, and again, result in a gentler restart.

Any technical guys have a reason for this advice?
find quality mono recording(s) and hook up each channel to diff. cable. place speakers in same small area of room. use balance control and listen long enuf to make it meaningful. repeat, rinse. :) fwiw, i once accidentally turned my tubes A/B UL off and on quickly and the resulting surge and noise did not make me want to do that again! i'm no no electrical engineer obviously but the manufacturer did not issue that warning for no reason. as noted above a/b cable comps can be done in a more helpful way anyhoo.
If you on and off your amp quickly it is very tough on your rectifier tubes.
Hi Jsman,

How is turning an amp back on before it is fully cooled down hard on the rectifier? If anything, a completely cold start is harder on the rectifier because the cold filament means low resistance (so, high in-rush current) and very rapid heating and thermal stress.