For scenes with lots of Poser imports or objects with large texture files, I found that turning off Auto-update on the camera preview makes a big difference.  While the camera updates, you could watch the resources start to drop.  As soon as I turned that off, resources were stable.  

This was a scene using about 7 DarkAnvil houses and several Poser figures  and props.  With Auto-update the resources would drop below 25% and I would get the warning (but no crash) on opening the scene.  Turning Auto-update off gave me around 76% resources on opening.  Big scene, big headache, but it's done and rendered.

Next time I do a project like this I will use multi-pass and make two scenes - one for the background, one for forground and people.  Read the User Projects article on e-on's site about how the Lirhful Station picture was put together. 

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