If I carry a full canister I can resort to only carry one. If I insist on using up my half-filled canister I have to bring two, because I can't really trust the half empty to work. As a result, there is a collection of half-filled canisters in my shed...
This is a common problem (half filled canisters laying about).
Several uses for half filled canisters:
1. Take 'em day hiking where you don't need a full canister and make tea or soup for lunch.
2. Use 'em with a micro lantern. Lanterns typically burn gas at a much lower rate than a stove, so that half full canister may last a good long time.
3. Take 'em car camping where weight isn't so critical. You can throw a hole bunch of half full canisters into your kitchen duffel (or box or whatever) and burn 'em until all used up.
4. Invest in a refiller (at your own risk, not a standard or approved practice) so you can top off your canisters.
HJ