timing

The "official" closing of the refuges is around the end of September. This is NOT a rule, so they might close earlier, like they did in 2008, or later if the weather is good and there many people walking (the refuges are a sort of business). Also, they don't always all close at the same time, so make sure you are ready for anything. I started walking on September 26th, and the staffed refuges were Refuge de Tighjettu and Refuge de Ciottulu di i Mori, In addition to Haut Asco (refuge and hotel), Castellu di Verghio (the hotel). I'd say, if you want to play it safe, start no later than September 10th (and carry at least 2 days' worth of food with you, doesn't have to be heavy, just something that will hold you over in case of emergency). In any case, during this period, there should be food available at Haut Asco, Vizzavona and Bavella.