Hawaii is proud of its marine sanctuaries — Papaha­naumokuakea Marine National Monument and the Hawaiian Islands Humpback Whale National Marine Sanctuary — and will be forever. These are two sites featured in a series of stamps marking the 50th anniversary of the national marine sanctuaries system, issued as Forever Stamps.

That means they cover the basic first-class postage for as long as you have them, even if the cost rises above the present 60 cents. So it makes sense (cents?) to buy a bunch.