I've done so much backing and forthing over the years, I'm now very quick at packing. I know what I actually need and what turns out to be bag fodder. For example, I no longer pack gym gear. Ever. It's a fantasy thinking I'll hit the gym when I'm on the road. If I have any down time, I'm sketching or playing my guitar. If I think I'm doing anything else, I'm kidding myself, and I'm not willing to use bag space or spend energy carrying things just to maintain my own delusions anymore.
Yep, we're down to essentials. The bag doesn't change much, whether it's a three day or a three week trip.