[Amps] Alpin 100/GU74b contest performance?

[Dick]

Hello,

I am rather unfamiliar with tube-based amplifiers, so therefore some questions:

Wonder if anyone has some in field experience in using the Alpin 100 amplifier in a CW contest, like CQWW.
How about cooling and advised maximum output power during an CW contest? (to keep it simpel: key down ... Watt?) 

Alpin itself claims an maximum output of 1100Watt, but that's with their for this amplifier choosen tubes.
I saw reports of people changing the original tube for a GU74b somewhere from the shelf, which delivered 200Watt less...
(around 900Watt or so)

So, I guess the original tube will alter, and so the maximum power will slowly drop too.
How about this.....how long will the GU74b capable of delivering the high outputs?

73

Dick, pa4vhf