'Wear' is a somewhat misleading term. Permanent magnets gradually decrease in strength, but this has very little to do with usage. The "life" of a permanent magnet depends on many factors. Naturally occuring forces conspire to knock the little domains out of alignment. But this is normally a very slow process. Temperature is a major player in this process. The higher the temperature, the faster this process will occur. Extreme heat [surpassing the curie point] will immediately randomize the domains. A sharp blow can also knock domains out of alignments, as can other nearby magnetic or electrical fields. Radiation can also knock domains out of alignment. But again, under normal conditions, neither your fridge or you will live long enough to watch the little fellow fall to the floor in exhaustion. At the quantum leve [e.g., electrons] magnetism is eternal.
By "quantized magnetization" I mean properties like the magnetic moments of the electron, muon, proton or neutron, and perhaps surface magnetic field quantum effects near a superconducting ring with Josephson junction.
In that case, you should make it clear what you mean, because the terminology you used is, by no means, typically applied to these cases. Magnetization is a statistically defined quantity - it is a property of an ensemble of particles, not the property of a single particle. You can talk of the magnetic moment of an electron, but not of the magnetization of an electron!
godd answer chronos.
But for generality, the fact that the fridge magnet is on the fridge (steel door). This will act in the same way as a keeper. Hence it will maintain its magnetism for a substantial length of time. More than if it was just resting on a table for instance. Of course, the domain theory will dictate its eventual downfall.