We recently purchased this to use on a trip (5-6 hours). It made things much better. We use the 4 oz. Playtex bottles with the drop-ins and our 5 month old eats every 3 hours. The warmer took about 15-20 minutes to warm the 4 oz. bottles. It looks like there's still a lot of butane left in the thermacell cartridge, even after four uses. You do notice a slight odor when using it inside the car, but it's not bad, and cracking the windows a little helps.Overall we were very pleased. This will make shopping around town easier and not restrain us to three hours. We're looking forward to using it on a short hike in the near future. The transaction from BabyEarth was smooth and they shipped really fast!