12 gigs? ouch... I'm on a Mac, so things might be a little different but the only poser related .tmp files I'm finding are in library/application support/poser/render cache. What I'm finding in there are the cached renders, the number of which files are determined by the settings of your preferences/render/cache/max cached renders. I have my prefs set to 10 max renders and max undo at 25.

You have me wondering now if there is some gigantic poser temporary file lurking somewhere on my computer. if you're refering to the cached renders you can trash those files and change your settings in poser preferences to a lower number.