Magnets and the Loss of Magnetization

Environmental degradation is a natural process

Depends on the type of magnet. Some magnets last longer than others. But even if they deteriorate with time, it take mostly a very long time, much longer than to become relevant. I was shopping for some magnets recently for a science project at a friendly college and I discovered that some of the better known magnet manufacturers publish a wealth of informative material on magnets. Try "exploring" with Google.