When you say:
"It's just the motion of the air."

Do you mean that the air motion causes the magnet to spin, or do you mean that some other motion caused that spin and is simply being slowed down by the air?

When you say:
"In a vacuum, it would spin for a LONG time,

I assume your meaning to be that the spin would need to be initiated by some means, otherwise it would not spin at all?

When you say:
but I think there are some kind of irregularities in the magnetic fields that would slow it to a stop eventually.

Do you mean the magnetic domain orientation or do you mean some other irregularities such as the surface of the materials?

Various physics experiments indicate that there is some type of a angular momentum associated with the interaction of moving electrons and magnetic fields, I assume that the electrons are moving within the magnetic material that is suspended in the magnetic field, could you explain why it would be impossible for these magnetic fields to interact in such a way as to create the rotating motion?

Johannes