They are always adding new content. Thought it's does have in app purchasing it gives way more away for free than most other games. And after years of playing I find that it's always something I can go back to and find there is always more to do.
Really loved the Pirates of Caribbean update and they also have the best holiday events of any game I have ever played. I spend Christmas Thanksgiving and Halloween playing this game.
The recent mermaid update even gives missions underwater!!!