D.R.
My daughter is 5yrs old and she says her food is still warm when she go to lunch at 11:45. She is using a stainless steel thermos. I boil water and the let it sit in the thermos with the lid on for about 5 or 10 minutes before adding fod. I also heat the food thats going in the thermos as well. HTH. I would also love to hear what others are doing.