I got a replacement today at the Apple Store in Brea Mall. First they wanted to troubleshoot the MBA to see the issues. Then they actually read the case notes. Then the "Head Genius" had to give it a once over blessing to ensure it was an issue. The "Head Genius" basically told me it was software telling it to go to sleep. It was showing Previous Sleep Code 5. He said the software I was running could be causing it or it was the laptop.
The customer next to me had an appointment for the same issue and we talked a little bit and you could tell the "Genius" wasn't happy with it. I was basically discussing my issues and what's coming up on the forums. The "Genius" told him it could very well be a different issue. But yet the issue I described to him was exactly the same as mine and your posts on here. You could tell the customer was more amped about the situation after we talked. It was funny.
Also, to see your Sleep Causes... launch Console. Under System Log Queries select All Messages. Then search by just typing in "previous". This may possibly help Apple Support if you can make note when it actually goes to sleep based on the issue we're all having Mind you, you will get this Sleep code when you set time puts it to sleep. So keep a note of that.