Ever wonder why Steam's Offline Mode never let you stay offline? Believe or not, this isn't intentional. Being required to periodically log on and verify your account is actually a bug, and Valve is trying to fix that.
As it turns out, the Offline Mode is supposed to be "indefinite," as in you can stay offline for as long as you wish. Sure, you won't have access to all of Steam's features, but the point is, you're allowed to remain offline forever.
Valve's Henry Goffin revealed this much when replying to a post on the Steam user forums. When someone mentioned having to log on every two weeks, Goffin replied:
This is not actually true - Offline Mode is designed to be indefinite. You can't access any of Steam's online features such as friends lists or saved game synchronization, of course, but the client should allow you to run in Offline Mode for as long as you like.
That said, there are many components involved in Offline Mode, and 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'.
It isn't an easy fix, either. Goffin goes on to explain that the system was created back when the Steam catalog only had a "dozens of games" available. Now, the devs have to deal with thousands of titles, and that's no small task.
Many of the older games on Steam were using an older authentication system which has many known issues with Offline Mode and is incredibly difficult to maintain - it was written for a time when there were dozens of games on Steam, not thousands. We are in the process of upgrading every game in the Steam catalog to a newer authentication system (and fixing bugs that result from the conversion), but this is a slow and time-consuming process. 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.
As to why no one knew about this before, Goffin attributes that to Valve having no community reps or PR staff. This means the staff has to use valuable time if they want to post on the forums -- time better off spent doing their jobs. On this, he wrote:
We have been working very hard on upgrading the underlying technology in Steam. We have no community managers or PR people, so all the time that we spend on forums is taking away from development time. That said, I know that it's frustrating to get no response, and it looks like we aren't doing anything about it.
Other participants in the thread have since expressed their gratitude for Valve's efforts. No doubt many of us are looking forward to that indefinite Offline Mode.