Answer:
I think you live beneath a roof that is upheld by me; I think you seldom walk abroad but my fair form you see; I close you in on every side you very dwelling pave and probably I'll go with you At last into the grave.
I've been around for millions of years, but I am no more than a month old. What am I?
What three letters change a boy into a man?
What goes all around the world but never leaves its corner?
I soar without wings I see without eyes. I've traveled the universe to and fro. I've conquered the world yet I've never been anywhere but home.
No matter how little or how much you use me, you change me every month.