this is the second thermocafe i purchased. The first one was GREAT. it keeps coffee or tea hot for 12 hours it was a DF2150TR16. This one the DF2150 doesn't even keep my coffee/tea hot until lunchtime.. and yes I pre heat the thermos before filling. My work hours are 930 to 530 so I fill this at about 830 and by 1230 the contents aren't even lukewarm. Either this one is a knockoff or those last letters in the model # make a difference. I am purchasing another let's hope the next one is like the first one. They are a little tough to keep the inside clean after many months of coffee use.