I have to say, I have a great mistrust of mystery shows. Especially when there's a core mystery. Most times they just keep pushing the answer down the road, because once they solve it, they have no more show. They are stretching what was probably a movie pitch or a novel into something that is supposed to go on for years. I'm thinking of Lost, Flash Forward, Under the Dome
Execution can certainly help, but, for me, when the core of your story is a mystery and you don't want to answer it for years.... then I find that frustrating.
Definitely agree. At the very least, if they're going to go that way, have something that can be answered within a season to go along with the core mystery so that people can have something to look forward to, because it certainly does no good if the show is cancelled and we have no resolution to the core mystery.
For me though, it isn't just the threat of cancellation that makes me want something resolved, I just don't think a mystery can be sustained (remained unanswered) forever. American TV for the most part is an open ended product (unlike a film or a novel)... they don't want it to end. So, if show relies on The Answer as your finale... how do you structure that? How do you plan? Your central drive doesn't become answering the mystery, but to put as much in the way of answering that for the characters.
If you can make a two hour movie out of your mystery show idea, then there probably really isn't enough for a show that is supposed to run for 7 years.