Is the apocalypse too depressing for TV?

Like almost everyone else, I loved episode one of The Walking Dead. So why haven't I got around to watching episode two yet? For that matter, why did I never get around to watching season two of Jeremiah, or those last half dozen episodes of Jericho? I didn't get more than five minutes into Survivors!

I've read lots of post-apocalypse books and comics, and watched lots of post-apocalypse films. Usually I love that stuff. Give me a radioactive wasteland and a band of hungry mutants and I'm happy as Larry. I don't mind being made miserable once in a while – it's bracing! – but I think I'm reluctant to sign up for something that'll make me unhappy week-in, week-out.

I don't think it's just me: I was trying to think of a post-apocalypse programme that lasted more than three seasons, and didn't have much luck:

The Survivors - 3 series
Buck Rogers in the 25th Century - 2 seasons
The Tripods - 2 series
Jeremiah - 2 seasons
Three Moons Over Milford - 1 season
Jericho - 1.5 seasons
Survivors (remake) - 2 series

Maybe the problem is that the apocalypse is a nice place for a holiday, but not somewhere you'd like to live. TV shows become a part of the fabric of your life, and perhaps the apocalypse isn't well-suited to that.

The only programme I've been able to think of that broke the curse was the remake of Battlestar Galactica, which began with a nuclear holocaust and lasted five seasons (if you include the mini-series). Perhaps because, although it was gruelling and miserable, it was so good you couldn't possibly miss it.

I'm pretty sure I'll keep watching The Walking Dead until they stop making it, but, like BSG, it'll probably be one of those programmes I save up and watch in bursts.

Have I missed any programmes that lasted longer? Is The Walking Dead doomed to a fatal second season drop-off in the ratings, or can quality win out, like it did with BSG?