Funny this topic comes up. We had an old can that we used this entire camping season. It ran out at the start of our last trip. We put a new one on and cooked twice before it was empty. I'll be plumbing a line from my main tanks soon.
We feel that the wind plays a big factor in how much propane we use.
Coffee in morning perks in just under 10 min. When just a little bit of wind going wrong way perk time has been as long as 15 min. We have several lic plates hooked together with note book rings that we use as wind shield for the stove burners, really helps. If your cooking right next to rv you already have 2 sides protected, so that helps. When using Dutch oven, the wind screen also helps in keeping charcoal from getting blown around.