No they don't go in circles. They flow pole to pole the best way they can, then back through their source. Most travels within the object and on its surface. About 10% or so gets above the surface, I believe. That is the weak stuff, and that is why it rises up. There is a more complicated secondary flow to that.<quoted text>
No, magnetic field lines always go in circles. No source point like for electric fields at a charge.
Why do you think they 'bypass' anything?
Actually, the magnetic field will gradually diminish with use. How this is relevant to space moving is unclear.
Magnets get weaker from the environment working on them, not the load. That is why they make keepers. You can consider those full loads. That field will last as long as the material does absent outside influences.