Mongol Logic.

After stumbling onto this site, I saw that the author mentioned thermos flasks (or "flarks" as they are called in North London) and their use in Mongolian yurts, thinking about it, it makes perfect sense really, rather than boil a bit of water every time someone pops in for tea and something make from horse milk, you boil a batch in the morning and store it, ready for use, in the flask. Maybe we have become so used to instant hot water all the time, that we fail to see the common sense in simpler solutions. anyone who has boiled water on a woodburner will appreciate the massive amount of energy needed to boil just one litre of water.
Anyhoo, this is my chosen flask, the Thermos Venice...
Obviously I filled it with boiling water immediately (after pre heating first) to see how it did. The answer is pretty damned good, it was filled with boiling water at 3pm, I dropped the thermopile into it at 10:30pm and it showed 76c, highly respectable, and that was after pulling enough water for 2 mugs of coffee from it. I'll do another temp check in the morning to see how it's doing.

*Morning*

10am and it's managed to hold 56c, that's about the same temperature as a cuppa that's been left for 15 minutes. Add in the chill factor of the mug, 56c isn't really enough unless I use plastic mugs from now on. Either way, 17 hours later and still steaming is very respectable.