Why does the ghost of christmas present grow older clearly older before scrooges eye?

Scrooge and the ghost travel through the present and as they move the ghost gets older. Time does not remain still, It was strange, too, that while Scrooge remained unaltered in his outward form, the Ghost grew older, clearly older. The change in the ghost is meant to symbolize that time is short:old age and death are close at hand, especially for Scrooge.