What I do is, when wanting to save an expression in PP2010, I go "Expressions", use the "+" sign to add the expression the library, entering an expression name and now, before hitting "Ok", I click on the "Select Subset" button. In this new menue now, I only leave the parts checked, I want to save in this set. Things I set up, like "eyes open-colse", "mouth open", etc .. Parts I don't want to be saved, especially things like the custom face morphs, I keep unchecked.

This way I only save the parts I really want and can use it the next time or on a diff. figure, w/o applying anything else.