He said twelve hours, then another twelve on top most likely. I think the reasoning was basically cut off Blaine's mind from short-circuiting by knocking him out and then hopefully when he wakes up, he will be more psychologically prepared to learn about the island and what's gone down with Kurt and stuff. Because back home, he apparently had a complete psychological breakdown after Kurt died.

I know you want to tell Kurt, but if you do, he'll want to get straight to Blaine and I don't know if I can cope with them both losing it. Because Puck is barely keeping it together either, seeing Blaine like that all over again.