Cas knew all about looking after the Winchesters and getting killed for it. It was nearly becoming a hobby for him, really.
He considered the question for a moment, holding his coffee but no longer interested in drinking it. "...Maybe. For a night. I wouldn't want to inconvenience you." He was tired though, and having a bed to just lie in for a while would help. He had been on the go for a year without stop after all.