User blog comment:Na299/Ways of Gold Farming/@comment-26348265-20150606221436/@comment-26335320-20150607064616

Its less than 20 days.

1st car  - 10 days time limited where new stage unlocks each day.

2nd and 3rd car - 5 days or less for each car as new stage unlocks when the previous is completed without waiting for day change.