It's a matter of comfort. If the insert comes out, fire the ball guy who glued it. But like every piece of equipment, it needs to be taken care of. New inserts are not expensive unless the pro shop is ripping you off. If you need them more than once every 5-6 months, I suspect something is wrong somewhere else.
Also they are VERY easy to replace yourself, with a small screwdriver and some Super Glue, if needs be. You can buy them online for anywhere from $1 - $3 each.
Oh, if yours fell out, didn't someone, anyone in your league or the center's pro shop have some Super Glue to glue it back in?? Someone always carries it where I bowl. Ask the guy who carries 6 balls to a league; he usually has everything.
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"Those who do not remember history are doomed to repeat it."