Only moments ago we told you that Apple released the iOS 6.1 Beta firmware to developers, and now iH8Sn0w has tweeted when the beta firmware expires. According to iH8Sn0w the iOS 6.1 Beta (Build 10B5095f) firmware will expire on Friday November 30th, 2012 at 8PM (EST).
Apple implemented expiry timers on beta firmwares to ensure developers who update to one of the beta firmwares either upgrade to the next beta or the official firmware when it is released. If you do no upgrade to the next firmware version in time your device will be placed in Recovery Mode.
At this time the only details we know about the iOS 6.1 firmware is that there is improvements to the Map Kit framework. As such, the only reason you should be on iOS 6.1 Beta is if you are a developer and want to test your application for compatibility or experiment with some of the improvements/additions.