My vote would be for SPRING. Aby kittens go through the "terrible twos" for months on end. Get ready. My only advice is to play play play with them during waking hours and hope that they sleep at night. They love to play, as you may have found out by now. My guys have one toy that I have to hide between playing sessions. It is a fishing pole for cats, with a little fishy attached to the end of the line. They go crazy for it and I can drag it and them all around the house with them in tow. Good luck. Hehehehehehehehe. Kittens!