The closure is 100% reliable. You can go there with your eyes closed! I have not really checked the holding time in the temperature but to go to work and move in the day, it seems to me correct. Hint: it is indeed necessary to use either as gourd or as coffee thermos. Alternate the two liquids seems to me impractical. I tried once to coffee at 8:00 am and 2 hours after cleaning, it was very difficult to do from the taste, even after repeated washing.