We typically do breakfast and dinner and a 1lb canister lasts us a whole weekend usually.
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Now if you hate the waste of throwing away canisters (though some people refill them - I don't think it's worth the time/money/hassle to do that) you can usually get an adapter that will let you run your propane appliance off of a refillable propane bottle - 5lb, 10lb or 20lb. You can camp for a month with a 20lb bottle and refill it at any RV park and at a lot of gas stations, U-Haul, etc. We've pretty much stopped carrying the 1lb throwaway cans and instead I just lug an extra 20lb in a milk crate. Yes it's heavy and bulky but then again, I drive a Suburban so storage space isn't exactly at a premium.