Neodymium magnets have a very strong magnetic attraction, and when plated with other metals that resist tarnishing and oxidization, will last a very long time. As long as the magnet isn't subjected to repeated or intense impact or stress. Neodymium itself will tarnish when exposed to air, and is brittle (compared to other elements like iron and iron alloys), so it can fracture or shatter if struck with enough force. That being said, it -could- work if used properly.
However if you're relying on centrifugal force to extend a sort of "plug stopper" simply using pins attached to springs would be much more practical, and the lack of magnetic properties would likely keep it from interfering with any electronic components that could theoretically be incorporated in the key and lock itself. The pins or bar used in this way could be designed to trap the plug at a specific point, such as back at the shearline, forcing the pin stacks to reset, or there could be multiple stopping points in the cylinder that will catch the plug and halt it thereby forcing the attacker to eventually reset the lock anyway.
In either case, if the picker is aware of the trap, they would still be able to defeat the centrifugal force needed to extend the stopper pins by not attempting to spin the plug until it's only a small distance from the pin stacks. The trap wouldn't engage until the pins had already passed the shearline so it wouldn't completely diffuse the use of a plug spinner, but could add another layer of security and therefore another obstacle that delays NDE attacks.
Just some of my thoughts on the matter
