I'm wondering about a suitable frequency for releasing a new game version, concerning bugs, new features, new levels, etc.
What do you expect from a developers point of view and a players point of view ?
Releasing a new version always makes a certain amount of users recall your app and delete it. Also very frequent updates can annoy people.
I suggest you deploying analytics. If you see that more and more users complete all the levels, or usage trends start to decline, I think then you should release a new version.