Just got my cooler bag a few weeks ago and I finally got to try it out. The reason I wanted the bag is A) Where I keep my fermenter a swamp cooler will not fit and I didn't want the mess. B) My man cave is always around 72 F so I needed something to help keep the temp down. C) I've been reading nothing but good things about these cooler bags.
Back to the bag.... For my second batch ever I made a ESB and finally got to try the cooler bag for the first time. I wanted to keep the temp around 64-66 F for the first fermentation... I used two 1 liter frozen water bottles I changed out every 12 hours, 6:30 AM and 6:30 PM. Also I left my blow off tube running to a bucket on the outside. Wrapped a aquarium thermometer in a towel and tape it in the middle of the carboy. I had no problem keeping my target temp range of 64-66 F, I got to 68 one time just because I got home late one night and didn't change out the bottles in time. After the fermentation I used one frozen 20 OZ bottle that I also switch out every 12 hours to maintain 68 F.
This guy works like a charm. I haven't had anybig issues with the bag. If your looking into one then make this a early Christmas present! It doesn't take up much space and it can hold a lot of bottles if needed. Just wanted to give my review on the bag and it's a winner in my book! (Only problem I had was to help with the airlock at the top I had to use a large tall cup to cover the lock. Also I should have used a smaller bucket so that it would fit inside of the bag but even so I didn't have a issue with keeping my target temps)