> they told me they haven't heard that they [Powermax canisters] will be discontinued anytime soon
This is my understanding too. Coleman know there are many of these stoves out there and that owners really love them, so Coleman has said they feel some responsibility on them to maintain the fuel supply.
Now, cold weather operation. The three gases used have boiling points as follows:
n-butane: -0.5 C
isobutane: -12 C
propane: -42 C
If it is too cold for one of the gases to boil, then any canister with that gas in it is going to have a problem. Obviously straight propane would be the best gas to use, but in hot weather the pressure inside the Powermax and screw-thread canisters would be too high for safety - see my article on exploding canisters. (That said, you can buy small propane canisters, but they have a different fitting and are heavier.)
So how well do the various gas mixes perform?
This shows how the internal pressures vary. (The curve has appeared in some of my other articles and also in the FAQ I maintain.)
Key point: once the pressure drops below 1 atmosphere or 14 psia, the canister STOPS working. And this is a function of temperature.
You can clearly see that the 60%n-butane/40%propane in the Powermax and the 70%isobutane/30% propane in the Kovea canisters give the best cold weather performance.
> Have you been using the adapter?
I have carried it on some shoulder-season trips when I was not sure about the weather. And it *was* useful when the evening temperature dropped below freezing a couple of times. I used my Snow Peak GST-100 stove on it.
> Are all the "new" powermax cartridges the same, or do you still notice the
> 2mm difference you mentioned in the article?
The change in profile of the Lindal valve fitting seems to be permanent. It is due to a change in the canister crimping machine.
> Are there any strength or heat issues with using aluminum braided lines?
Well, there shouldn't be. After all, the hose is not meant to get very warm, let alone hot. But the metal braid is vital to protect the plastic hose inside and to prevent it coming adrift at the ends as well.
But I have not seen the stuff you are referring to, so I have no idea whether it might be suitable or not. I don't even know whether it could be made gas-tight.