I have been pleased to note that, after moving in with my girlfriend, I have "infected" her with my anti-clutter mindset. I try to live by the general rule of, "If I haven't thought about it in 6 months, it shouldn't be here," and it delighted me the first time I saw her with a box full of old odds-and-ends and explained on her way outside, "I haven't thought about or used any of this in years."

Your note about not being immune to the "stuff treadmill" (great term, btw) rings true to me, too, though. Because of our cultural upbringing, it's incredibly easy to get caught up by the consumerist undertow.

I was inspired by George Carlin's rant on "stuff," which someone transcribed here:

http://www.writers-free-reference.com/funny/story085.htm

It's less endearing without his delivery, but the idea is the same: we get emotionally connected to our stuff, and in many cases, that isn't conducive to removing stress from our lives. I think he also touches on the (somewhat pernicious) assumption that Americans grow up believing, which is the assumption that everyone is "supposed" to want and have a big giant house filled with all kinds of tchotchkes. I may some day own a house, like I said in my OP, but I never want to have so much stuff that I couldn't fit as much at least half of everything that isn't furniture into the back of my station wagon. No specific reason for that particular measure of proportion... it just feels right.

Other than the "6-month rule," I just try to be brutal about every individual object I come in contact with. I try to occasionally remind myself to ask, "How does this thing improve my life and make me happier?" The answer could be as simple as, "Looking at it makes me smile," but if it really doesn't do anything for me, I put it in a box, and--as with before--if I don't think about it for 6 months, it fails the test and I get rid of it.