Does a knife sharpener ever need to be replaced?

I have a Henkels hand-held, counter-top sharpener that I hold with my left hand while pulling my knife through it with my right. It used to be a snug fit for a knife, and I'd feel some resistance. Lately I've noticed lately that it slides quite easily, and there's no tension. Is this normal? Is it still effectively sharpening my knives? Should I replace the sharpener?