It doesn't require much thought to work out that carrying three weeks food is plain and simply mad. I do have a Lowe Alpine 65l rucksack that would swallow my kit and two weeks food but why?
Last year I walked Hadrian's Wall Path and used a 45l rucksack, in which I fitted my kit and six days food, well the tarp tent and thermarest were strapped on the outside at the start. Unfortunately the rucksack wasn't up to carrying that kind of load - not it's fault it wasn't designed for that sort of thing. (Gear heads - it was a Berghaus GR45.)
This got me thinking about how much I'd be prepared to carry and with what. I bought a Gregory Z55 last summer because the hipbelt would cope with the load and I 'd have a couple more litres of space for longer or winter trips. However I never really got on with it; I just found it impossible to pack to my liking, bizarre as that might seem. So I started looking for a replacement for the Berghaus but with a hipbelt to cope with the weight of my kit and six days food, and some pockets to put munchies in.
Bob at BPL mentioned that the OMM Villain might suit as you can replace the back panel with a 3/4 thermarest and I was sold - there's one less thing strapped on the outside for a start, and a weight saving too. It has a host of other features that I could rave about but I'll post a review under 'Gear' at sometime.
So rucksack sorted and a decision on how much food to start off with made.