I tried again before I left for work today, and it only took 9 shots before stopping this time.
For the purposes of this intended collection, I'll always be near 110V. The UPS is an APC Back-UPS RS 1500 with a sidecar extra battery and has been working fine for more than a year with my home computer. I just gave the camera a try with a capture every five seconds, and at 200+ pictures, it's still going strong.
The point to this project is to get me 24 hours from my window at home, which has a view I'm fond of. At work I'm in a windowless office, and although I'm inundated with digital clocks, they don't give me any visceral sense of of the time of day. I want my computer screen background to be the view from my window at home. I don't have disk space for a 24 hour movie, but I do have software that can fade from one photo to another, I settled on one photo every 10 minutes because that seems to capture the change in light sufficiently when it's changing fastest, at dawn and dusk.
I have two hypotheses for the failures:
1. Even though the camera has external power, the batteries are signalling that they're getting weak and it shuts itself down for that reason. I'm going to try removing the batteries from the camera and run exclusively on external power.
2. The maximum amount of time I can set before the view screen goes blank after inactivity is three minutes. Perhaps that transition to screen blanking is botching something. Once the screen blanks, I get no indication at all that the camera is taking pictures, although for a while it still is. I'll switch to one photo every 179 seconds to try to prevent the screen blanking.
Neither seems likely to me, but I am very much a newb.
I'm going to try again for another 24 hour run; that should just fit in the the 3.6Gbyte I have free.