This is the first show in literally forever that I haven't gotten tired of by the end of season 3. I don't know for fact, I think they had the entire storyline planned out from the start, which is the right way to tell coherent story on TV....
I'm fairly certain that Gilligan said all along that they had the major story arc planned out from the beginning and that it would take 5 seasons to do it. I commend them for sticking to their guns and making, what I agree, is one of the best tv shows of all time. Because they could keep cranking them out for awhile and I'd still watch them.
a lot of people say Breaking Bad and The Wire are their two favorite shows of all time. My problem with The Wire is that of its 5 season run, 2 of the seasons weren't very good (2 and 4). Breaking Bad has been excellent from start to finish.