I like this brief description from an anonymous contributor on that site:
"If you are going for weeks (any time over one week), you only need 4–6 of any clothing item. When kids were little, and growing fast, I'd buy 2–3 lightweight, quick-dry (convertible) pants and tops, and plan to do laundry. That, and one pair of walking shoes, one pair of sandals/water shoes, PJs, a bathing suit, a fleece, a hat, and a good roll-up rain jacket has taken them all over the globe. I'd often have these in their closet set aside especially for travel."
Update: Here's what we ended up with: 4 or 5 interchangeable outfits each, almost all elements of which are fast dry; bathing suits; five pairs of shoes between us; as many books as we could justify, plus our Kindle loaded with classics, France-related material and K's online class books; two inflatable air pads (which aren't as comfortable as our regular self-inflating camping mattresses but are MUCH more compact); a Thermarest Tech blanket (very small, very thin sleeping bag) for each of us; one meal-kit each; toiletries; my SLR camera and two lens; K's point and shoot camera; and a few games. I forgot to take a shot of it all packed up in our two rolling knapsacks, each of which also sports a removable day-pack but will do so when we are ready to depart NA on Thursday.