While clicked on a figure. Edit/Figure/Geometry/Remove Smoothing Modifier
That's what had an effect on my render times.
Daz is strange, from 3 minutes to an hour thirty is a real jump. I'm interested to hear of your results using the method above.
In answer to your question about doing the background separate. The game I'll be starting soon would be too complex for that. Thinking about it, I would do that if the game was less complex. Drop shadow was fairly easy thing to do when I was using the likes of photoshop.