[Amps] Estimating CCS, I CAS, Plate Dissipation by Eyeball 4-400As

[Patrick Barthelow]

Friends, 
I have always been in admiration and awe to watch a Glass tube QRO Amp in full song.
In the case of 4-400As or 3-500Z tantalum plates, wile  being a teenager-ham, I tended to wince a little at those two tubes showing what is probably long term sustainable CCS plate dissipation.and usually backed off on drive to see a more "dull red" tantalum (not talking here about carbon plates)
plate, which looked safer to me.   
I found two good photos of  4-400As,  commercial modulators, and an RF PA  at full song, or  maybe at near, (conservative)  full song. here:

Modulators;   Bright Orange:
http://hawkins.pair.com/atcitynj/atcity14b.jpg

RF PA;   Dull Red;
http://img153.imageshack.us/img153/7161/2collins20vtubeslitsize.jpg

I wonder if  more seasoned eyes than mine could characterize these two photos of  4-400A Tantalum plates.
If say, the Modulators were dissapating  400 watts each, and bright orange,  how many watts, would you guess the RR PAs were dissapating?

The Modulators are described as being at CCS dissipation ratings.    Apparently they could operate for years, 24/7 at that level.  Is that true?  or are they being pushed, hard, and will live a shorter  (how long) life?

The RF PA tubes, look to me to be more comfortable, more safe for long life.

Also, is there more wear and tear, that cuts into long term life in amateur service, of the 3-500Z or 4-400A family, where the tubes, in correct SSB service, or CW service, are dissapating widely varying power, according to duty cycle and use?  In SSB, to go from "cool, idle" to 2KW PEP and back several times a minute, is that hard on the tube?    I would guess they would be happier in, say 1 or 2KW FM broadcast transmitter and staying orange 24/7 than in amateur service.   What say?

73,      Pat Barthelow   AA6EG