I took the Joemo XL to work yesterday. The tea stayed hot for several hours, until I drank it all up! After my late lunch (we were busy) I rinsed the Joemo, poured in the ice from my soda cup, and added water from the water fountain to drink as I worked. I finished the water pretty quickly. At around 11 pm, 8 hours later, I realized I hadn’t emptied and washed my Joemo. Opened it up and VOILA! The ice was still there! Pretty much all of it! Yes, this puppy insulates!