I classify my food bags in Liter sizes---so for a six day trip I would probably take a single 20 liter sea to summit silnyon UL bag.
Without resupply on a 21-24 day trip I take one 20 liter bag for my cookables (stuff to cook---dinners mostly), one 35 liter bag for my snackables---and a third long thermarest stuff sack for my loaves of bread and third food bag.
Food bags are disposable items and I've been thru dozens over the years. In the old days I used sleeping bag stuff sacks.
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Here's a typical long trip load---about 50 lbs. Very difficult to get much bear line height without climbing rope and a pulley system.
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One time I met Sgt Rock and his son on the BMT near Slickrock Creek.
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Rock just started going UL and here's his hung food bag for a 5 day trip. HA HA HA JUST KIDDING . . . it's his bear line throw weight.