Very true about the combination of multiple magnets. Over the short-term, it does help to increase strength. However, when they remain bonded and are moved or excited, perhaps there is a metal object around them in storage that would aid in the movement of the particles. It could be wiring in...
Ok, the answer is simple. When magnets come in close proximity of each other, they move the magnetic properties of the other, creating a magnetic flux. As this flux occurs over time, the magnetic properties weaken. It doesn't matter if it's an NeFeBr magnet or a regular ferrite magnet, it will...