I find that I can pack the same for a week or longer as I do for a long weekend. Laundry on the road is no big deal. Shoes and outfit to suit different settings is something I've been able to work out over time, so now I've got a couple of things that I automatically reach for when I am traveling and know that I might want to dress up for dinner.

The toughest thing I've had to face as far as packing goes is changing climates (e.g., -30C in Edmonton to +25C in the Dominican Republic). Going from a cold place to a warm place, I end up with clothing that I have to lug around for my entire trip but I know I'll want them at some point for the trip home. Thankfully, down is light and compresses well!