There is no such thing as a maintenance-free deck. Wood decks, just like those made from composite plastics and other artificial materials, should be kept free from dirt, oils and mildew.
If water still beads on your deck after rain or being sprayed with a hose, you probably do not need to reseal the wood. If the water soaks in, reapply the same water-repellent finish you used the first time or find one that is compatible.
If you are refinishing a deck with a semi-transparent stain, apply the water-repellent after the finish is dry.