All this talk of riding faster left me wanting to push myself this afternoon due to the nice weather out. I took some pointers that I read here and taking into account the comment about varying intensity, I decided to only do a half hour instead of my usual 1+ hour, but to ride at a higher intensity.
I was able to maintain and average of exactly 15.00MPH for 32 minutes, which seems like a big improvement over my first week or so of riding. I also noticed that I was able to bend my elbows and crouch into a more aerodynamic position and maintain a speed of over 17MPH with about the same effort it takes to maintain 15-16mph in an upright position, so that's another pointer I will definitely be using!
I'm going to try riding at that speed for longer and longer until I can easily maintain a full hour, then try to up it even more.
I read a lot of advice, but it seems like the main thing you guys are telling me, in a nutshell, is what one poster said: "ride more"...sound about right?