Its a never ending quest. Even now that I no longer back pack I still remain interested in new and old developments of reducing weight and compacting my gear. I have used some of those plastic compactor bags with the valve. They do work well but are a little on the heavy side for a carry. None of the plastic bags lasted very long but would certainly last a 5 day touring ride in a pannier.

There is always something to learn when discussing and viewing how people pack in and out. Even when looking at travelers from 5300 years ago...
Ötzi's 3,300BCE Gear List ? The Vintage Hiking Depot.