My kitten's 7 and a half months old and has just started to slow down from completely manic and totally out of control to acceptably lively! He's just started sleeping when we sleep, although he gets us up early at the weekend as he doesn't get the idea of a lie-in He's resting as I write, but it's about 34 degrees C here in Italy, so I think he's a bit warm. He'll go bonkers a bit later when it cools down a bit. Four months is still very young so I think you've got a bit of a way to go yet!