Sorry I can’t help you as to a specific manufacturer but I have found that pre-heating the flask helps to hold the warmth a little longer i.e boiling water in the flask for a while then replace immediately with your chosen drink/water.
I use stainless steel flasks filled with water for the actual activation with a good old glass lined Thermos flask back in the car to use on return.
As Allan says warming the flask prior to filling makes all the difference. 1 litre stainless steel ones - even from supermarkets - are better for most circumstances like dropping. In winter I leave mine on the storage heater when I get up on the morning of an activation, get ready and fill the flask last thing. Will stay hot for hours even in sub-zero temp until you take some coffee (other hot drinks are available) the effect reduces and the liquid cools a lot quicker.
I have always been going to put tiny wee polystyrene beads in the gap between the two layers to aid with insulation but haven’t got around to it yet but I presume it would help a great deal. Someone on here has probably tried it.
Slightly off topic, but I recently bought a tiny butane/propane burner from Wilko (other stoves and suppliers are available). This, plus a 100g gas cartridge, plus pietzo striker, plus pan, plus double skinned stainless steel mug from local outlet store, weighs just less than my empty Thermos 1l stainless steel flask.
It is more of a fiddle to use, of course, but you get proper tea each time. Also, you can boil up stream water, which reduces the water reserve that you need to carry on a long walk.
Having said all that, I recently lugged it around the Brecon Beacons only to find that I’d forgotten to take any tea bags :o) Doh!
On topic, I meant to say that I have had a cheap unbranded stainless steel flask fail after a couple of years. I didn’t drop it or anything, but it slowly became less efficient. I guess that the metal to metal seal where the base cap is welded on was not perfect, and air leaked in to the vacuum space.
I replaced it with a Thermos, but the construction appears to be the same.
John - yes, I liked the look of the Jetboil, and even more the Primus offering of similar design. My bits were a lot cheaper, though, and pack up smaller.
Incidentally, whether I use flask or stove, I only carry or heat water. Other ingredients are added to the hot water in the mug. That way, I never have to wash up the flask or the pan :o)
I just purchased a 1l thermos flask in prep for winter from amazon only cost £9.99, tested it yesterday at work after a 6hour drive coffe was still hot but will soon see how it performs in the winter.
Also got myself a highland hip flask for the overnight stops from backpacklight.co.uk
I have a small stainless steel flask with about 50 cl of single malt in it. I’m thinking of downgrading it to a blend, because I have been known to tie a wire around the neck of the flask and chuck it over a tree branch. Single malt deserves more respect than that!
You get what you pay for. I use a 1 litre stainless steel flask. You can pick these up very cheaply, but you’re better going for a more expensive one. I once prepared soup in mine on a Saturday morning and forgot to take it out on the activation with me. I forgot about it completely on the Sunday. I ended up taking it to work on Monday and having it for my lunch - still piping hot.