This page of the Mr. Prepper guide tells you how much time you need to complete the game.
The first playthrough without using a lot of tips will take you about 15-20 hours. The second playthrough can be completed in 5-6 hours.
The game has no time limit. If you still want to play, don't build the last (fourth) stage of the rocket, so as not to advance with the plot. The following achievements are connected with the game length (counted in the days survived in the game):
- It's just a start! - survive 15 days,
- Novice Prepper - survive one month,
- Intermediate Prepper - survive 2 months,
- Advanced Prepper - survive 4 months,
- The Original Prepper - survive a year.
- Speedrunner - complete the game within a month.