OK! I give up- I cannot pack for a 30 day trip with carry-on only.   After 13-14 packs and un-packs and discarding most of my clothes, reading materials ertc, I put the backpack on and made it halfway across the room before deciding I was not dragging all that weight around the airports.  I added a small bag to my collection  which helped distribute the weight and means that I can actually find something in my pack without having to pull everything out. If I need to I can still carry the larger pack(which does have rolllers) on  my back, the small pack on my front and the small bag around my waist.