THREE RHYMING RIDDLES

1)
The young often need me,
But they usually must wait;
I provide a wealth of knowledge,
But always just too late.

2)
Defining the boundary
Between this and that place,
Most often am I
An open and shut case.
To a semi-circle or less
Is my movement confined,
Your privacy is that
For which I'm designed.

3)
I have covers, but I'm not a bed,
I have a spine, but I have no head.
I have leaves, but I'm not a tree,
I'm of great value, but can be used for free.


Answers:

1. Experience
2. A door
3. A book