It took me 179 days to beat the game, with difficulty set to Easy for most of the time, and several (I think 3) prestiges.
The claim is that the game is balanced around no prestiges :/ uh, how?
It is balanced around no prestiges meaning that all battles are beatable on normal without any prestige bonuses.
There were also a bunch of people who completed the game before I even made the prestige system, so I don't know.
Admittedly, I have never played from start to finish in one go to time it, but it took me 3 weeks to reach mid-point I believe (on normal), so I expected the overall time to be close to two months.
Did you play in the Idle mode or incremental mode?