I am one thousand five hundred years old!

I can remember when he was just 500 years old, then 700 years old when the old series ended.
900 years old in the new series and now 2,000 years old.
If he was 500 years old when I was a child and he is now 2,000 years old, then I am 1,500 years plus!
And I don't feel a day older than one hundred and eighty!