Agree on minimizing pre-planning, and that 90L seems quite big. 40L is probably a good size for basic ho(s)teling gear. Personally, I prefer to travel with 65L, so I can add: light tent, sleep pad, sleeping bag, micro stove, 1 pan, water sterilizer. This obviously allows me to include hiking trips within my travelling, but it also allows something even more valuable: when you want to hitch hike from place A to place B, and there's not much in between, you don't have to ask 'can we make it in one day?', you just say 'if we dont make it, then we'll make camp, and start again the next day'. Removing the 'must know where I'm sleeping' constraint is tremendously valuable and liberating to me (as is true for removing most big constraints).