JEEZ!!! Are you also afraid of the sky falling??! Nothing like maintaining a defeatist attitude to maintain a peaceful existence. ("it's working great, for now. But, I know it won't last".)
Are you also afraid of your refrigerator dying, washer hose connection failing, or toilet tank cracking?
Everything (especially man-made) has a finite existence. There's no use in troubling yourself over it. If it's working correctly and is properly maintained, enjoy it and simply deal with any issues that arise AS they arise.
If you're worried about your fish, in the event the filter should suddenly fail, keep a back up resource on hand (ie: sponge filters, HOB, air pump/stones, etc.). That's a sound idea no matter what filters you're running.