Oh definitely. When presenting for university I'm always given double the time to present. I remember for one presentation, we had a time target of 20 minutes, I got 40. In practice, my presentation took me 15 minutes fluent. During the actual presentation, I was stuttering so badly. I cut out most of the wider explanations and stuff, just saying what was absolutely necessary. Even then, one hour later I was only 2/3 of the way through when we had to break for lunch. That sucked.