Answer:
Longer than a decade and shorter than a milennium
I am the yellow hem of the sea's blue skirt.
The buyer doesn’t want it, the producer doesn’t need it and the user doesn’t know their using it.
What can't you see, hear or feel, until it’s too late. What shadows love, and shopkeepers hate?
It is where kings, queens, knights and bishops go to war together.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?