Do magnets wear out? Can a magnet ever wear out or lose strength?
If you break a magnet it (seemingly) gets weaker, but what about from normal use?
Or even very heavy use, like placing 2 magnets facing each other, so that they detract from each other, does that strain cause it to wear quicker?

(Note, I'm not looking for a merely yes or no answer; If yes, what will cause it to wear out quicker or slower. If no, why?)
 A: This is a corrected version of my deleted answer.
Magnetic material can be magnetized, i.e. all the tiny magnetic domains  (in a ferromagnet for example) can become "permanently" oriented  by using a strong external magnetic field. One then has a permanent magnet that has potential energy stored in the orientation, an ordered structure . Similar to a crystal structure , which is stable until external effects supply energy to destroy it .
During magnetization of a material, there is what is called a magnetocaloric effect, which shows that the process of creating a magnetization  is exothermic.

The increasing external magnetic field (+H) causes the magnetic dipoles of the atoms to align, thereby decreasing the material's magnetic entropy and heat capacity. Since overall energy is not lost (yet) and therefore total entropy is not reduced (according to thermodynamic laws), the net result is that the substance is heated (T + ΔTad).

This article  summarizes how one can demagnetize a magnet:

Demagnetize a Magnet by Heating or Hammering
If you heat a magnet past the temperature called the Curie point, the energy will free the magnetic dipoles from their ordered orientation

Heating and hammering can happen when the magnet is used to mechanically move objects, or in a dynamo, due to friction  and induced magnetic effects in surrounding materials
......

Self Demagnetization
Over time, most magnets naturally lose strength as long range ordering is reduced. Some magnets don't last very long, while natural demagnetization is an extremely slow process for others.

This is due to thermodynamic processes as at any temperature in a solid there are vibrations and rotations which generate black body radiation and loss of orientation.
......

Apply AC Current To Demagnetize a Magnet
One way to make a magnet is by applying an electrical field (electromagnet), so it makes sense you can use alternating current to remove magnetism, too.

This reverses the process that magnetized the material.
Perpetual motion machines which use permanent magnets all can only work until the effects of demagnetization from friction, heating, and stray magnetic fields (if an attempt is made to extract work) , will demagnetize the permanent magnets.
A: Yes, a magnet, as time passes, will lose part of his strength. There are two main reasons: 


*

*Thermal energy: it causes the disorientation of the atomic magnetic momenta.

*If you have a bar magnet free in space it’s easy to see (using Ampère’s law) that there is inside it a magnetic field $H$ opposite to the magnetisation of the magnet. In order to avoid this phenomenon you should anchor it (that is to say “linking north with south pole“) with a ferromagnet. 


This two phenomena will cause atomic magnetic momenta to disorient, and, in so doing, the magnetic strength of the magnet will decrease.
The demagnetisation happens even if you apply a sufficiently strong magnetic field opposite to the one generated by the magnet.
EDIT: 
The proof of the existence of a field $H$ inside the magnet is now reported: let’s take a bar magnet as shown in figure 
The Ampère’s law tells us that 
$$
 \int_\gamma H ds =0\; .
$$
Now let’s call $\gamma_1$ the piece of curve inside the magnet and $\gamma_2$ the piece outside with length respectively $L_1$ and $L_2$. The Ampère’s law becomes
$$
\int_{\gamma_1}Hds +\int_{\gamma_2} Hds =0\; .
$$
Let be $H_1$ the mean $H$ field inside the magnet and $H_2$ the one outside. The integral turns into
$$
H_1L_1+H_2L_2=0
$$
From here we have 
$$
H_1=-\frac{L_2}{L_1}H_2=-\frac{L_2}{L_1}\frac{B}{\mu_0}\;
$$
And here we have what was to be demonstrated.
