Cora has slept through the night at about 3 weeks old. Now she usually goes to bed at 11pm (we are night people) and wakes up at 8am, gets fed and then sleeps for 3-4 more hours. That is already A LOT of sleep. Last night however she slept from 6pm-8am and then went back to sleep for 4 hours after being fed!!! Today she was fine and active and happy like usual. still 18 hours?! It's nice, don't get me wrong... Should I be concerned?