You need A LOT of wood to keep a fire going for days.
That's kinda my point, if you have to cut it all you're going to be pretty bushed. But in Canada in winter perhaps that's your only choice.
"Construction," on the other hand, could require a more precise division of the wood.
What are you planning to build? I can't think of many things I'd want to build that require a precise length. Although my imagination doesn't go much beyond a brush shelter. I've built many of them and never needed a saw and probably seldom even broken anything to length.
I'm not trying to be combative here, just trying to figure out what I'm missing and if I DO need a saw I better start carrying one!