Cycling is an endurance sport and the longer your race the more important it becomes to increase your endurance. Unfortunately it takes a long time to develop that endurance. As a matter of fact, some cycling experts suggest around 24-30 weeks of "base training" every year to improve your performance/fitness level!
You will need to progressively increase your training load during this period to adequately develop your base fitness (including rest days and rest weeks).
In my opinion 4 x 1 hour and 2 x 2 hours are equally ineffective to prepare for any long distance, multi-day race/tour. You are essentially training your body to become really good (fast, efficient, etc.) at riding no more than 2 hours twice a week. How would this possibly prepare your body to be able to ride for more than 2 hours, 6(?) days straight without being able to recover properly?
I doubt that pro cyclists would log as many km as they do if there were a "quick fix" to building endurance.