If you updated your iPhone, iPad, iPod or Apple TV to the latest iOS 5 Beta 3 release, you need to know that, according to iH8Sn0w, it will expire on August 18, 2011 at 8pm EST.

So what will happen at that time? Well, your iPhone might explode, your iPad will implode, and your Apple TV will fly back to its original factory in China. More seriously, I’d assume that it wouldn’t let you use your device until it’s updated to a newer beta or maybe even the official firmware… 

This process can’t be stopped because it happens at boot level, and there’s currently no boot-level exploit for iOS 5. At any rate, make sure you updated before that date to avoid potential issue.