I suggest that you really need to learn to "eye-ball" the covers on your balls. I say that because I believe Magic Shine has some grit in it. That means unless you are very cautious in using it too often, you will change the amount of polish/shine on the ball, making it the actual surface (the "grit") finer and finer.
Unless you have VERY high revs or bowl on very worn lanes (both of which will chip away at the coverstock anbd wear away the polish/shine), you only need to touch up the surface lightly every 20-25 games or thereabouts.
SIde note:
Be aware that we're in the season (for most of the US) where humidty is starting to increase and while the ball's reaction seems to indicate more oil, it's just the increase in humidity that's causing this reaction. You may or may not need a slightly stronger ball (maybe the solid version of this pearl), while the lane man may say he has not changed the amount of oil he is applying.
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"None are so blind as those who will not see."