Why does the ghost of Christmas present grow older before scrooges eyes in a Christmas carol?

The Ghost arrives on Christmas Eve 1843, his life began on Christmas Day 1842. The life of a parent Christmas Ghost is only one year long and then as each new Christmas brings with it a new Christmas Spirit. It is after the Ghost reveals teh two children , Want and Ignorance" that he tells Scrooge that his time on this earth approaches its close.