I thru hiked the whole Pyrenean High Route last year, from the Atlantic to the Mediteranean. I noticed that canister gas for stoves was very patchy. There are very few towns or villages on your way, if you stick to the proper route, and then very few gear shops in the towns when you do get to one (varies from 3 to none). Sometimes a food shop will have canisters, but different shops sell different makes, and sometimes they are plain out of stock. Some people were carrying enough canisters for at least two weeks at a time to get round this, very heavy.
I took an alcohol stove, the Trail Designs Sidewinder Inferno kit with the Starlyte stove and 600 ml pot, total weight 5.5 ozs, using max 1 oz fuel per day . I picked up or saw alcohol in Hendaye, Arizkun pharmacy (ask for the 96% ethanol kept in the back), Aldudes, Lescun, Gavarnie, Vielha (posted my ice axe and crampons home from here, alchy from last garage on east edge of town) and Bolquère.
The great advantage of the Inferno design is that you can burn wood if you do happen to run out of fuel. It’s fun anyway. If desperate when going above treeline you can carry a few sticks.
