How much time does Naka or Carlsen need to beat a lesser player?
If you have time to wander around and look at other games while you are playing: the time is too long.
If you have to take bathroom breaks: the game is too long.
Naka or Carlsen needs a fraction of the time. The only thing that matters in chess is skill. This is why they have simuls. Time is virtually irrelevant. Thus: don't waste so much of it.