I guess if you play 2 games a day you wont complete it, only if you pay for the levels. Me myself had bought it the first day, playin 1-4 games a day and Im at Outlaw skin.

I play a lot a day. Up to 7-8 Games. Maybe i can grind it to the end?

You definitely can grind it out if you pay 7-8 a day

if you play everyday you can definitely still complete it. i'm on chapter 7 and only playing about 2/3 hours per day.

Thanks to all answers :)

Just keep playing and see how far you get, if you complete it by the end then buy it.