(Yes, this is going to be a discussion about sequels and prequels and such.)
Constant Readers must know by now everything I've done has been volume 1 in a series of 1. it's a habit (no better word for it, I think) I slipped into right after I completed Summerworld, the first offering from Infinimata Press (or, Genji Press, or Glinebooks as it was known then).
After Summerworld came out, I spent about a day mulling over possible successors — Autumnworld and Winterworld, with all the implications of downfall/death/eventual rebirth encoded into those titles. But the more I turned it over in my mind, the more I realized I'd said everything I wanted to about those characters and that world, that even talking about how they might pass things along to whatever successors might arise wasn't that interesting to me. What I really wanted to do with that story was leave it completely behind and do something new that had nothing to do with the previous thing.
Still, I'd spent enough time thinking about the implications of writing sequels to get why this is done. You want to save up the really good stuff, or at least tease people into thinking there's more Really Good Stuff waiting in the wings, because profit margins in publishing are terribly small, and any way you can keep people coming back is worth it. You don't want to blow the whole wad at once.
There's even an argument to be made for this on the noncommercial/indie level, where profit margins are less of a concern than personal integrity. It's hard enough to get anyone's attention these days, so you want to hook them with something that stands out. And hooks themselves are scarce, so once you have a good hook you want to get as much out of it as you can. The economy of attention is even less forgiving at the bottom end than it is at the top.
But again, I come back to my motives. Why do this, and why do it this way? I don't write because I want the biggest audience, but I do want the most faithful one. I need it all the more at my tiny scale. (Hello to my loyal readers, all six of you.) So maybe doing things in series serves me best after all, to keep them coming back. Thing is, this is only true if you assume loyalty's not possible any other way. "From the people who gave you ____" has a lot of draw.
Now that I have reflected on it, there is one more impulse I find driving all of this. It is the feeling that in life there are no guarantees, that even tomorrow is never a certain thing, and that it only makes sense to go forward wherever you can. I don't know how much time I have on this planet. Longevity and a general hardiness run in both sides of the family, but that may well mean nothing. And there's always the chance a fire tornado could flatten my house or a plane I'm riding in might drop into a volcano. No guarantees except the moment I have now, typing to you.
Knowing all this, I would rather opt for a legacy where I always chose to do something new than keep doing something safe.