How and when a mother decides to wean her baby from nursing varies greatly.
With Mr. P I weaned him...cut him off at 19 mos. He was waking once a night and I'd bring him into my bed to nurse him. The final straw for me was when he let go of the booby, said "I shirsty (thirsty)", and proceeded to take a big gulp from his water cup that he brought with him. After his big gulp he went right back to nursing...burrrr!
Today I think I had the same sign from Baby George. He was nursing and let go to quickly pop a piece of bread into his mouth...a piece of bread he had locked up and hidden in his little fist. Then after chewing for about a nano second he went right back to nursing:) Sheesh!