The suggestion actually catches him off-guard, and it takes him a solid few minutes before he's able to do anything other than just stare at his brother. He'd been expecting another disagreement about him using himself as bait, or maybe even a suggestion about Dean being the one to flush them out. But not this. Not an actual retreat.

"Weren't you the one who suggested a hunt in the first place?" Granted, it seemed like it'd been mentioned more as a way to unwind some tension; something that'd happened as soon as he'd disappeared off that hour to go feed. He eventually grins, actually seeming a little amused by it all. He's not happy about the idea of calling of the hunt this late in to the game. But if that's what Dean wants, he's not about to ignore it. "You couldn't have said that before we left?"

...it probably helps that he knows he can always come back later to finish the job.