that's a great average speed. If you drop your average heart rate you can do another 20 for sure. I did a 130 mi ride last year by simply taking my time and keeping fueled up. At some point the challenge becomes just a matter of how fast can you do the 100 mi. I could not keep a 16mph average up for even 80 mi so kudos to you. It's only a question of finding the right heart rate/speed to allow yourself to do 100 or more miles.
BTW..the home made energy bars didn't happen unless you post a recipe...