Answer:
You can have it, and be at it, But it never lasts forever.
What instrument plays from the heart?
What is between heaven and earth?
Once you know it exists, it no longer exists. What is it?
If you are unsure how to use one then just ask a flight attendant.
If itβs information you seek, come and see me. If itβs pairs of letters you need, I have consecutively three. What am I?