No, if that were the case she would be a teenager before she weaned!
DD was 12 lbs at birth and is now 5 years old and 37 pounds. We were so glad she had tripled her birth weight by 5 y/o.
I cant imagine how old she will be when she hits 60 pounds.
DS is 25 pounds (was 12lbs 2 oz at birth) at almost 14 months. His weight gain is slowing down like dd so i dont think he will nurse till 5x birth weight either.