Wow. When one gets tired of answering the same old question, maybe it would make sense to pass it by! 
OP - I think you are right on track with not shipping these pressurized items in the extreme heat. And it is true that they are not shippable by air via the USPS. So, it's good that you inquired!
I've had soldiers & Marines tell me that they receive them just fine (from other people) in the colder months though and not understand the concern/vigilence of AS supporters on this subject.
Here's a thread that you might find useful: http://forum.anysoldier.com/forums/t/34.aspx?PageIndex=1 I found it by typing "Pressurized" in the search box. You can try other thigns to find other existing discussions.
Have a great day!
cj/