As of now, the record for the longest use of a magnet space wheel is 44 hours and 20 minutes.

there is no magnet but there is a wheel

electromagnet

Reverse the polarity of the magnet.

Take a look at the picture by using the link to the Wikipedia article, then come back and read the answer. The wheel has a steel axle, and it also has magnets built into it. The magnets keep the wheel in contact with the track on which it rolls. The operator need only time the movement of the track to keep the wheel rolling.