> To me canister stoves are really 3-season stoves. The inverted versions work RELIABLY
> in "cool" weather (down to freezing). Reliability is the key word.
With all due respect, I suggest that the key part of this statement is 'to me'. After all, many of us who spend a lot of time in the snow do use canister stoves, with great success and great reliability. All the time.
It has been suggested that you can only use an inverted canister stove down to about -20 C. That is only true under worst case conditions. If you are carrying a water bottle in your pack and it hasn't frozen, then clearly it has not got below 0 C. Most likely the warmth of your back has helped a bit here. If your gas canister is next to the water bottle it is probable that it has not got much colder than 0 C either. In which case the ambient temperature of -20 C is not really relevant. Once your stove has started running it is no problem to keep the canister 'warm', like around 0 C. Overnight – keep it tucked under or inside your quilt/SB. Yes, it's a vital item.
> survival experts agree that you should carry three types of igniters. i.e. storm
> matches, 2 lighters and something like Firesteel and a block of magnesium.
Carrying more than one source of fire is undoubtedly good. But whether that has to be more than one type of source is quite another question. I carry storm-proof matches sealed up and two Bic lighters. One of the Bics is also sealed up. I have never had to get out either the second Bic or the matches. (The latter have been sealed up for 20+ years – why do I bother to even carry them?)
The 'block of magnesium' idea is just plain raving stupid, for several very good reasons. The first is the obvious question of how do you light the darn thing? For that you need a source of fire. But if you have that already … The second is the problem of lighting a 'block of magnesium'. Has anyone ever tried this? It is almost impossible without a gas torch, and it conducts heat so well. Now thin magnesium wire – that can be lit with a Bic and some skill, but if you have the Bic … The third problem is what in the blazes do you do with a burning lump of magnesium? It's going to be way above 3,000 C: how do you hold it, where do you put it, what do you do with it, and how do you extinguish it? If it came into contact with your body it would simply burn straight through you.
Mind you, I do carry a very small sealed capsule of Esbit chips. They can be used to help start a wood fire in extremis, but again I have never needed them. Vital? I doubt it.
With all due respect, I suggest that those self-styled 'survival experts' are mostly irrelevant couch turkeys. Those guys spend all their time setting up disaster scenarios each of which only requires a (different) kilogram of gear to handle, and which will never happen in real life anyhow. The fact is that so many of us have handled all sorts of extreme conditions without any of their gear. The one thing you really need is the ability to stop and think. After that, ordinary walking gear is quite enough.
Cheers
;-)