What setting do you have for the undo/redo?  I have mine set to 1.  There is also another button on the File Options page to flush history.  That helps me get back a few percentage, not really enough to make a difference.  After all my flush, purge, etc, I get back most, but not all -  about 10% of my start resource level can not be recovered.   Why some models suck it down to OOM levels and can not be recovered from is what bothers me.

LVS - Where Learning is Fun!  
http://www.lvsonline.com/index.html