Another alternative to shortening your commute is to drive to a parking lot, leave your car and bike the rest of the way to work. Then in the evening just bike back to the parking lot and drive the final leg. Of course that is dependent on finding an appropriate parking lot, and doesn't save as much gas, but if it is what it takes for you to ride, do it! If you are going to do the ride in one piece, starting out with drive/ride/ride/drive is a good way of building rest days into your routine. Even though I'm fairly fanatical about riding even in the winter, there will be days when you may need a break. Sometimes the combination of work and biking can be too much and you need the extra z's, or just the time to sweep the floor before you leave. That is especially likely to happen with a long commute so don't be worried about driving occasionally.