Store eggs upside down or not? This may be an odd question, but someone told me it's better to store your eggs upside down (the pointy side down).
The explanation was that there's an air bubble on the bottom of the egg that wants to go up.
If you put it upside down, the pressure on the membrane is less and it stays longer.

Is there any truth about this?
By "it stays longer" do you mean that the egg stays good longer or the membrane/air pocket stays around longer?

I don't know why you would care about the air pocket so I'll go with the other.

Orientation is not going to noticeably affect egg quality. I don't use egg cartons. I store my eggs in plastic tubs (carefully). The eggs end up in a random orientation and there is no noticeable difference between any two eggs.

I have heard to people storing the eggs differently to center the yolks in preparation for boiling. This is purely a cosmetic thing.