+1 - And not to forget, it's not unheard of for a local agency to figure that if CBP holds you for 2-3 days while the "consider their decision" that's more time than you would serve anyway. So, they just let you sit and then eventually they let you go.
As I understand it, CBP does not award stay credit, bonus points or the like, but you do get all 3 meals included for the price of the room.