Where would you add a night for this trip? For August time northern Spain

Currently we have 1 night Gijion area, 1 night Oviedo , 1 night Santander , 1 night Bilbao , 2 nights San Sebastián

We driving along the coast from Oviedo to San Sebastián. Would it make more sense to add a night maybe in between Gijion/ Santander like Llanes? Or add another night near Bilbao? Or maybe spend one day in pico de Europe which we currently don’t have planned