Fastness can be applied to anything.
Characteristics of this person can be:
- likes a fast-paced life (in general)
- likes things to be done quickly
- doesn't like to waste time
- doesn't like to spend time on things that may take too much time
- if things get slower or if they are not done as fast, he loses enthusiasm
- likes people around him to be fast also
- likes fast machines/animals (ex: fast cars, cheetah, peregrine falcon)
- likes fast internet (who doesn't?)
It is not as simple as being:
- slacker (irony?)
It is like a life style. There is a term "speed freak" but it is too exaggerated and it has other connotations as well. I'm not sure if there is a word that exactly fits but at least it can be as close as possible or a phrase.
fast and furious?
Edit: He is not in hyperactive state. He can enjoy relaxing/keeping calm at times and spending time on the things he likes. It should not be associated with a disorder, it should be associated with a life-style or a culture maybe. Or just a characteristic feature.