I hold up my hands - it took me two attempts to get into Homeland, but once I did get hooked, I was fully under. I thought 24 had done everything that could be done with terrorism action drama, but Homeland brought an uncomfortable edge to it that made it fresh. You never knew how it was going to twist, and the characters were so badly damaged there were no good guys and no bad guys. The relationship between Brody and Carrie, mixed with the awesomeness of Saul... it was prime first season steak.
Then Season 2 came along.
Now, Season 2 of Homeland is still better than a lot of television out there. I powered through it, enjoying bits of it, but wondering what had happened in the off season to make the vibe change so dramatically. We had gone from something very fresh and original, to something much closer to 24, and seemingly already running out of ideas. So what happened? The answer is the artificial extension of an idea.
To explain, let's look at a number of other shows which had an outstanding first season, only to tail off as the years progressed. "Prison Break" is one such show, and the explanation of this is the easiest - he broke out (SPOILER! Sorry, the show is a number of years old now - keep up). How do you continue on a show that goes beyond the natural length of the original idea? "Prison Break" did at least manage a decent second season by radically changing the format into a chase show, and that worked. But in reality that was just a new show with the same characters.
"Lost" is a classic example with a slightly difference twist - I for one am bored to tears of people saying "well it started well but then it just got stupid". The idea behind "Lost" was one of the most intriguing in many years, and created a show that maintained the sudden surge in quality we hadn't seen before. However, as we got into the second season, it became obvious that the original idea was being stretched and in some places broken to form something much longer than originally intended. The show (in my mind) turned out OK, and was largely enjoyable thanks to a great cast. But if you took Season 1 on its own and compared your enjoyment to the whole series, you start to wonder "what if they'd carried it on like Season 1".
But the point is they can't - if you have a great idea for a TV show, that idea cannot be stretched or pulled or twisted, as to do so breaks that idea and creates a new, manufactured one that no longer has the sparkle of the first. This is why shows rarely have a mid or end series season that stands out - it's always a fresh idea which forms the first season that has any chance of brilliance.
So what's my point? That we should embrace first season greatness, and if you love it, watch it, buy it and treasure it. If the rest of the series fails to live up to that greatness, c'est la vie. It won't harm the first season. I promise.