Steam client "should allow you to run in Offline Mode for as long as you like" say Valve

Tom Senior at

The fact that Steam requires you to pop online once every few weeks is a bug rather than intentional design according to an official forum response spotted by Blue's News. "There are many components involved in Offline Mode," writes Valve poster Henryg, "some of them have known issues and bugs which we are continually working to improve. We're aware that it doesn't always work as flawlessly as we want it to, but please keep reporting bugs with Offline Mode. It is not broken 'by design'."

He also mentions that Valve are in the process of converting every game on Steam to a new authentication procedure. "Some day soon, once this work is completed, we will eliminate the old authentication system (represented by the ClientRegistry.blob file) and Offline Mode should immediately become much more robust."