Game Informer were invited by Valve to check out the first in the line of episodic content for Half-Life 2. They got the opportunity to play through Episode One in its entirety, shoot a video interview with Valve's Episode One Project Lead Robin Walker, as well as get details on the future of Half-Life 2's episodes and much more.
"The original Half-Life took two years to develop. Half-Life 2 took six years to develop. By Valve’s estimation it would take 18 years to complete the work on Half-Life 3."