Just for shiggles, I'll suggest a badge. Actually, a couple of them everyone would already get(have), but are trying to get RID of:
First badge could be called "Ending of the Story" Badge(in reference to "The Never Ending Story, somehow, and badge image may reflect this), where one obtains it at their first badge (or maybe a day or two after) because they are on their way to collecting badges elsewhere, but have NOT collected all badges possible(in normal game-play that is). (Or maybe lose it JUST as they obtain the next-to-the-last badge obtainable with some message like "Well you managed to get so many badges, you don't need "Ending of the Story" Badge. I guess that ends that story of this badge, huh? Keep looking!"
The second badge would be obtained when one finds half of the badges(or a day or two later) obtainable by normal game-play called "Center of Gravity". It would have an image of a spiral galaxy and the following message upon receiving it: "Well you got half of the way thru the badges, but there are more to go. I wonder where they are?" When the "Ending of the Story" Badge vanishes, or a day or two later, this badge vanishes with the comment: "I wonder if there is a story behind these badges? Will it ever end? Keep looking, just to be sure!"
Obviously there is room for tweaking into the actual storyline of the actual game.
When you do the best you can it's called a try!
If you don't you need to ask yourself why?
Just give it a thought,
And failure is worth naught.
And then like an eagle you shall fly!