Any tips for getting clearly tired babies to lie down, stay lying down (and not stand up again instantly) and go to sleep? J thinks standing up is such a fun game that he will not stop doing it, and won't sleep in his cot during the day any more. :-( I'd hoped once the novelty wore off he'd improve, but he's been standing up for a good 3-4 weeks now and it's showing no signs of improving.