Not really an answer to your question Sam - my friend obtained it form a US website but I don�t know which � but I heard on the radio last week that there are to be (at least) 7 series of Lost. Apparently the writers have a goal of where they need to get to by the end and have been commissioned to get �there� by the end of Series 7.
Now, I managed to watch one episode in Series 1 before losing it. I understand there are about 25 episodes per series, at least an hour long and one or two, two hour specials. So lets say 30 hours per series. x 7 series = 210 hours, or 26 8-hour days (assuming you sleep for some and work for the rest). Practically a whole months evening viewing!
And I bet, even after that everyone is still�. Lost.