The idea is to have freemium games that are completely free as long as you maintain a streak of passing at least one level per day.

When your streak ends, you would lose progress (e.g., a passed level becomes "unpassed" for each day that you don't pass a level).

You would only pay to avoid having to replay "unpassed" levels.

Do you think this model would be successful? Has it already been used in some game(s)?