If you started in SJPdP the walk to Zubiri is hard because it follows the day(s) over the Pyrenees. I would definitely recommend staying in Ponte de Lima the night before Rubias. It is a delightful town and you won't be doing a long day along...
6 Camino's arriving in Santiago, twice in May, once June, once July, once Sept and once in Oct. and saw it every time. It seems that more often than not, one of the tour companies is paying for it.