I registered at 9.05 for Les Gets on the sunday and 70 places had already gone. So pretty quick for some places. No one seemed to have chosen Avoriaz though so there is likely to be options still available.
how long are tickets usually available for before they sell out
In 2008 we bought Sunday tickets from Torgon 2 weeks after registration opened (bit rubbish as a start point but better than nothing). Les Gets/Morzine and Chatel will all sell out today I think, I suspect Saturday will sell out first, then Sunday and finally Friday. I am trying for Champery or Morgins.