Hi, Paul,
A lot depends on how far you walk each day of course, but you might be able to make it from Aviles. I think Aviles is probably a little under 300 km from Santiago. It's well connected to the bigger places nearby -- lots of connections to Oviedo and Gijon for instance. If you don't want to push it that much, I think Luarca is a very do-able ten days to Santiago. And Luarca is a very pretty town on the coast, a nice place to spend a day. Who knows what kind of weather you'll be in for, but Buen Camino if you go for it! Laurie