I didnt know there was a limit to skills and that once you learn a certain amount, everything else takes longer.
Because of that I started with the less time consuming skills and left the more advanced ones only for when I went to bed or the test period ended.
It would be really great to have a way to reset the skill tree. Maybe each skill should cost points according to how much time it takes to learn it so when you reset the tree you keep the points and allocate them however you please.