I can't upvote this enough. I love limited or mini series for this very reason. There are too many shows that just coast after creating an idea or mystery where even the writers themselves have no idea where it's actually going. These type of shows survive off cliffhangers and shock events and would continue on forever so long as people are watching.
I really wish more shows would just end tieing up all loose ends before the final episode. If the show is that great they can start a new story arc either with the original characters or a spin off in the same world. Any show that requires a cliffhanger to keep people engaged isn't great to begin with and will likely end in viewer disappoint. That's just my opinion though.