Hey, really glad you liked the game! :)
Actually the time you take doesn't matter, we just wanted to tell a little story everyone can enjoy and play their own way depending on which upgrades appeal to you. If you really want you can just finish it without any upgrades.
However once you're finished or during your regular playthrough you got the option to turn on the timer in the options and compete with your friends for the fastest time (we did that a lot during testing :D)