Okay, I just wrestled my aforementioned Daz scene into a state of more submissive submission. There are still 2 characters in the scene, Anneka and Will, with high-res textures on their bodies, clothes and hair. But I have reduced the number of props in the scene to 30 [from 60 — mostly I got rid of a lot of individual books]. Also I slashed the size of most of these texture files to about 20% of original size and dropped posability information from the props that didn’t need it. [The stuffed animals don’t need to be posable; they just need to sit there and look cute.]
As a result, now a render of the entire scene [OpenGL, 8 passes per light] takes 40 seconds, rather than over 60.
Hiding everything except what will appear in the frame gets the rendering time down to 18 seconds. I’d like to have it render instantaneously, a la digital camera, but that won’t happen unless I get a more powerful processor or start reducing the resolution of the characters themselves, which I refuse to do.