It turns out that the entire series was conceptualized as a novel at first which explains why it has such a coherant and well-integrated plot. Everything was designed to have a beginning, a middle, and an end instead of just fumbling its way from episode to episode like most serials. There's almost no comparrison to any show I've ever seen. Even all of the various star trek franchises were, at best, planned from season to season, with a bunch of gaps in there for filler episodes or segways into new areas. At times, the person who wrote the season finale was not the same person who wrote the season opener for the next season, nor did they actually communicate. It was simply up to the new guy to take the plot threads that he had been left with and try to weave them into something that wouldn't suck like crazy.
Really though, you can't expect any series based program to plan out multiple-year storylines. It'd simply be too farging expensive as an initial cost. Not to mention it's a huge risk considering just how shaky the success of any tv program is nowadays, forget the fact that it's sci-fi on top of it. Think of how many shows get canceled nowadays afte less than a season on the air, and it's no wonder that studios are usually unwilling to invest that heavily up front.
Anyway, I'm around a third through season 4 at the moment which by my calculations puts me at around 64% of the way through the whole thing. I've been watching the episodes like I expect there's going to be some sort of massive final exam at the end of it. Oh well, I'll leave this with a Lorien quote that I've always liked.
We've lived too long, seen too much. To live on as we have is to leave behind joy and love and companionship because we know it to be transitory, of the moment. We know it will turn to ash. Only those who lives are brief can imagine that love is eternal. You should embrace that remarkable illusion. It may be the greatest gift your race has ever received.