One huge benefit I've found from doing pomodoros even when there are no ugh fields and when I'm sufficiently motivated is that it forces me to stop and take stock of what I'm doing. I'll suddenly notice that I'm hungry, or that I have to go to the bathroom, or that pandora stopped, etc. All of these seemingly minor things often have a huge effect on my productivity. In addition, during the break I occasionally realize that the approach I'm taking to a given problem is all wrong. Breaks allow me to catch these mistakes often hours earlier than otherwise.