It really depends! In many cases, you can choose between a couple of different options, one longer and more scenic, the other shorter and a bit less interesting. In my recommended stages (see
book page 11 in this sample), it runs roughly 190km between Ribadeo and Xubia, on the outskirts of Ferrol. But, there are ways to make it substantially longer.
Speaking broadly, you can find some sort of accommodation every 20-30km, though Teixido is the tricky spot. Worst case, you might need to use a taxi to get to/from an accommodation on a particular night, but it's workable.
Check the Mar section of the forum for more details! I've posted there a fair amount, as have a handful of other Mar fans. And
Magwood's blog is an amazing resource.
For those sticking with the Norte, I'll make the pitch that you consider spending two nights in Ribadeo. On your "day off," leave your pack in your accommodation and make the stunning coastal walk to Praia das Catedrais on the Mar/Cantábrico, enjoy the famous beach, then take the train back to Ribadeo. A perfect little change of pace!