After I finished in SdC and walked to Finisterre and Muxia, I walked one leg each on several other Caminos as I wound my way back to Barcelona. I asked for sellos on all of them, handing them the same credential (well the last one) I'd already used, that had the sello from SdC as well as others...no one blinked a eye, or said I needed to have a fresh credential, although I wasn't staying in albergues. I guess albergues might question it, but if explained I'd like to think they wouldn't care. In fact, the only scrutiny my credential ever got was at SdC, probably because as he glanced through he noticed sellos from three different routes in almost random pattern (CF, Norte, Primitivo, CF, Norte, Primitivo, CF ), but a bit more looking at dates, then looking closely at the last 100 km, he shook his head, shrugged, and finished the paperwork. I always stayed my first night jumping caminos in a hotel, so the first albergue I stopped at could see I'd been on the road for at least a day , and no one asked me why two days prior I'd been on a different camino...but I may have been lucky.