Certainly, recurring themes can be good, and I most definitely have them, because, collectively, all of my stories on AFF, so far, have been different angles/aspects/periods to the same general over-arching story. I specifically date my narratives too, more for my sake if I need to read a previous story, to see when something happens, for consistency, which I try to maintain between my stories.
However, the nature of television, with the uncertainty on getting contracts renewed, and pressure to stay within the patterns of previous success, is most likely why Star Trek, and similar shows fall into the trap of stagnation – Star Trek even has some gag flowcharts out there that are spot on, with effectively insert $alien, $danger, and $technobabble, and it becomes alien-of-the-week. With writing, we’re not on multi-million dollar budgets, but instead in our free time, so we don’t have the same pressure for repeated performance. (I’d reckon that professional authors, though, could fall into the same trap if they’re getting overly pressured from their publishers.)
Well, admit I don’t follow that one too closely, otherwise the sex scenes in my stories would be few and far between ….
However, for the overarching main story in my universe, it is my field of expertise, so I could figure everything out in way too much detail; thus, I do ballpark calculations, and be happy with nice, round numbers.