If the arrow spine is not correct for you and your bow, you should be able to notice it at 10-15 yards already (bare shaft). The only thing I can suggest is doing the test keeping the bow straight. In other words, do not cant your bow when testing the bare shaft.
Also, if you are shooting carbon, you might want to test each shaft before fletching it. It should not be a big problem, but it takes a minute and ensures that the nock is aligned with the stiff side of the shaft.
That being said, everything wear out sooner or later. I would say, if the side plate wears out in less than a year I would start looking for the cause.
Just my 2 cents
Max