You've got some good tips in there, PoppaC! I spend several hours at a time as well, and I think I figured out what the deal was.

Typically I do a test render or two, and when the poses and such are up to snuff, I export to Lux via Reality.

Reality and Lux handle massive geometry with ease, whereas Studio does not, as it seems. This scene had very little in memory, but I think the poly count is what killed it, added with a V4 with SubD. Oops... 

I check task manager randomly to see what all is going on, and Studio does have a habit of running in 'Ghost' mode, where you've shut studio down yet it lingers in memory, sometimes up to 600MB even when you closed it a long, long time ago.

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