Why does William like to play when it's time to sleep?

Nowadays when it's time for bed at night, William becomes very playful after his milk. Last time, he'd finish his milk except for 1oz (he does this most of the times and I tease him that he's a typical chinaman like he's drinking tea - the saying goes that if you're chinese, you should leave alittle tea behind on your cup to show abundance) and then roll on the bed a bit and fall off to sleep on some part of my body.

But for many nights now William would do this after his milk. He leave 2 to 3 oz behind, out of the 9 oz that we make for him. Then he rolls around the bed, sometimes too near the edge and he enjoys my adrenalin rush as I quickly reach out to grab him. Sometimes he would let his head half fall from the edge of the bed whilst I hold on to him and try to drag him back. The boy also runs around the bedroom, playing with the curtains, walking on the bed, or just running up and down laughing away.

If I pretend to sleep and lie beside him, which I always do, he'd poke my eyes. Or climb all over me. Then put his buttocks right on my face for me to smell. Yes. This little supposedly-gentle-demure-looking boy. He enjoys sitting on my belly like he's riding a horse, or even doing push ups on me. Haiyoo, sometimes it can look quite obscene.

After all this, I entice him with the balance milk and sometimes he finishes it. Then it's back to play again. Mind you, all these while when the lights are off, the classical music on and no chatting. It takes me one hour or more before I put up the white flag, and message hubby for rescue.

By the time hubby takes over, William is too tired to protest and I secretly sneak out. Phew. Then... it's time to put Victoria to sleep.