Will Neodymium Magnets Lose Their Strength Over Time?
Barely. A neodymium magnet that stays below its maximum operating temperature, dry and undamaged loses only a tiny fraction of its strength over decades; you won’t notice it in normal use. When magnets do lose strength, the cause is almost always heat, corrosion, physical damage or a strong opposing magnetic field.
What Actually Weakens a Magnet
Heat
Above 80°C (176°F), standard N grades lose some strength permanently. Above about 310°C (590°F) they lose it all. Temperature limits
Corrosion
If the plating is breached, moisture rusts the iron-rich magnet. Rust flakes away magnet material and adds an air gap. Preventing rust
Chips and Cracks
Magnets that slam together can chip or crack, which removes material and exposes bare metal.
Opposing Fields
Forcing two strong magnets together north to north, or placing a magnet in a strong opposite field, can partly demagnetize thin magnets.