I use this bag to take bottles of breast milk back and forth from daycare/work to home. My commute is usually 30-45 minutes and they stay cold. I've been using it for about 4 months now and I haven't had any issues with the temperature. My only complaint is that the threads in between the sections are starting to come apart, but I think this is because I use wider bottles - Phillips Avent. I think it will still last me for quite  a while though. Overall, I'm satisfied!