Question

Why can't magnet be used as an energy source? They have a unique trait compared to all physical objects discovered today, and that a force present and in a good type magnet in a fairly conservative environment, that force can last for over 100 years.

So why can't it be a source of power?

Answer 1

Note: Magnet do not produce energy by themselves. They simply create a force field that attracts things.
In fact, we use magnets in producing electric energy, but that doesn't mean that magnets themselves produce energy.
Using magnets to produce energy is akin to using the earth to produce energy. And the earth gravity covers more objects than magnets anyway.

Answer 2

@Shadowys to add another fact... When a magnet is applying its force over a distance that means work is being done energy is present. A magnet has F but what's missing is D only. Or motion.