It took me 14 days from Aviles to Santiago including a day off in Ribadeo. I could have walked it in 3 days less but i was in a frame of mind of why rush my remaining time on the Norte, some camino friends i said good bye to in Ribadeo walked that section to Monte de Gozo in 5 days, that included a shortened section of staying at Miraz and Sobrado dox Monxes.
The options from Aviles seem to be walking either walking 11km-24km days or kicking on and doing 32km-41km days a fair few people do the latter. Just a word of warning about the Aviles to Cudillero/ Soto de Luina section, its not wellmarked and it felt quite tough in 2010, i wouldnt start going for longer sections untill you get after Luarca, there is sufficient albergues at intervals to be able to alter your day lengths as you need.
Buen Camino
Mike