Have you done much play after 90 stars? I ran endless once and got over 200 waves before I gave up on respawning my troops.
Gameplay after 90 stars?
The main thing I do now after completing everything is either beat my score on endless, or just simply try and complete levels on my criteria.
I would say give us about 6 weeks for the update - that should give you a lot more game (including New Game+, which basically doubles the length of the game, and in a non-trivial way that will hopefully be fun!). Ultimately though, this isn’t World of Warcraft. It’s a game that is meant to be played and beaten and will eventually end. I’m almost tempted to drop the “Endless” modes and give them ends (about 200 waves or something) just to avoid people spending absurd time on it when they should go find another great game to play. 
By another great game, you mean another game you guys made? 
Come out with a second episode with more units, equipment options, and levels… I’d buy it right off. :twisted:
(Am already L40, 90 stars. )