I've seen several people speaking about cracked eggs on here.....

I don't think so I have cooked in temperatures lower than -20ºC and I am sure it cools down even quicker.  I think it might just be that a certain percentage have a manufacturing defect and are susceptible to cracking.

Just my 2¢

Gerhard

I am one of the ones with busted Eggs...that are repeat offenders. Don't think it has anything to do with thermal shock. From what Bruce, the warranty guy at Egg told me your "standard" base crack is from the air intake to the rear. Thinking g behind this is the vent is the weak spot. I have had 2 XL bases crack like this. My Large base cracked in a way that Bruce has never seen before. It is about the shape of a half moon, perfectly shaped. On the inside of it there is a depression. It almost looks,like this may be how the bases are removed from the molds....they are grabbed by a clamp of some sort. Bruce is questing that my Large base may have not been fully cured when it was grabbed. My latest crack...well...this is in another odd spot. This was the first time I used it. Ran it 275* for 10 hours. Cooled, relit it to warm it up so I could clean it...let it run at 500* for a bit...until I seen it drippingoes grease. No rain on either day it was lit, both days in the 60's. 
I have pretty much given up. I understand about the warranty. I am tired of dealing with it...for now. Truth of the matter lifting these things with my clapped out back isn't doing me any good. 
In my case I can sum this up to having a dark clouds that follows me. If it can go wrong...it will...just a matter of when. I had every intention of riding my chopper this summer...but with the past several months being what they have been decided against it...not ready to die just yet...

they are tested by heating with a leaf blower thru the bottom until 1000+, then drenched with cold water.

i myself have on multiple occasions, including at and eggfest, emptied the meltwater from a cooler into the egg to cool it down quickly for transport.

the cracks all seem to start from the vent, and so that may be a weakness. or imperfections in the casting.  it's likely related in some way to the high temps, sure, but not because it goes from 200 to 700 quickly.

the dome temp isn't registering the temp of the fire itself, or even the ceramics.  it's the temp of the air flowing thru it.

I had used our original XL for several months with the cracked base. I had 0 troubles maintaining 225*. Granted I was using a controller. But out of curiosity I cooked a few times without it...still had 0 troubles. Only thing that did happen was some smoke leakage when I first lit it....and this obviously was due to my shutting the dome early. And if something greasy was cooked...and the grease managed to find its way to the bottom of the Egg it dripped out. Which is how I found out about my latest crack...I seen some puddles on the table under the Egg. 
The day I found the crack in our Largest base was "pizza day"....Ernie had already made the pizza so....ran the Egg up to 700* with no issues....have several times...