Another aspect that would help with longevity is content. It takes quite a bit of time to build background - most new ventures and almost all new games have a very loose universe that they just patch stories on. It works for a while but tend to end up as meaningless noise, fillers for whatever new quest or adventure. I'm not saying you have to create an entire Tolkien compendium of literature, but it helps to have a solid "creation story" for your world that would already set out overarching themes for latter content.

Do you have an idea on how you would continue to generate and build on your story?