I was stationed on a submarine, and as you may have guessed, coffee is a way of life. There was one particular tank that was kept at 120 degrees at all time, no matter what. I realized that if I didn't finish my coffee on my six hour shift, I could just put my mug down on top of this tank and let it sit there. When coming back 12 hours later, the coffee was at a perfect temperature, and ready to drink. That tank was my best friend on that boat...