Or you could just take care of your sub. Make sure they're comfortable; if they're about to pass out then you didn't properly take care of them and you should've probably let them out multiple hours ago. Also, don't ever leave your sub locked in a cage when you're not at home; that's a huge no-no. The only way this could ever be useful is if you're an extremely bad Dom. The sub should enjoy themselves, not just barely surive