Rob Mills sent me this interview with Rod Serling. He has always been an impressive writer, not only for his creativity but his prodigious output. On IMDB he is credited with 148 episodes of 'The Twilight Zone' over 5 years. Twenty Six episodes of 'Night Gallery'. It is astounding to think of this kind of creative output. He says 'it lacked consistency'... no shit.
Having written on a few Television series I'll tell you it's hard work to come up with creative ideas over and over again. Many days are spent staring at walls (or the back of your eyelids). I've always been drawn to feature films as they are one-offs and usually have a bigger scope (although this is changing). You develop an idea, you write it and then rewrite it until you're happy. With television you are always trying to expand the idea sometimes to the point of 'jumping the shark'.
On the last television series I story edited I said to the writers that episode 20 to 26 were going to be the toughest. This turned out to be true as predicted. It's hard to be original over and over again, especially when you are trying to out-do yourself every time. I think the only advantage that the 'Twilight Zone' had was that it wasn't locked into a single concept or a character. You could really reinvent the show every time. Still... 148 episodes. Wow.