Answer:
No matter how little or how much you use me, you change me every month.
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it can neither see nor feel it. What is it?
Thousands lay up gold within this house, But no man made it. Spears past counting guard this house, But no man wards it.
What loses its head in the morning and gets it back at night?
In Paris but not in France, the thinnest of its siblings.
I fly to any foreign parts assisted by my spreading wings. My body holds an hundred hearts Nay I will tell you stranger things when I am not in haste I ride and then I mend my pace anon.