It is a tricky question because one can consider a several day ride or just one day ride. And even considering one day, it is not the same stopping for lunch or using a mountain bike than a road one. In any case, my longest ride was a 60Km along the northern coast of Catalonia, just a few Km's from the French border. It took us all day leaving from Roses, but we stopped for breakfast in Cadaqués and for lunch in Port de la Selva.