Changing the composition only delays the inevitable; no coin design or denomination lasts forever. Eventually, the cent, nickel and even the dollar will be rendered so worthless by inflation that they can't make them out of any kind of material and still be profitable. At that point they either have to reform the currency or stop issuing that denomination.
And if they kill the low-value coins from circulation, I hope they kill them from the sets as well. There's nothing more pathetic than a denomination that lingers on in "mint sets" long after it's been withdrawn from actual use. A "mint set" should contain examples of the coins actually struck for circulation, preferably using coins pulled from the actual production run and not some idealized fantasy set containing coins specially made just for the set. If I wanted that, I'd buy a proof set.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis