Embark on a Costa Rican escape in your 20s with affordable flights, lively beaches, and lush rain forests. Discover Japan in your 30s, from Tokyo's bustling streets to serene Kyoto and snowy Hokkaido slopes. In your 70s and beyond, explore South Africa's wildlife, cultural gems, and historical landmarks in comfort. The definition of a dream vacation varies from person to person, but no matter how you define it, everyone deserves to go on a big, once-in-a-lifetime trip. But where do you even begin planning such an epic getaway? Chances are the vacation you fantasize about in your 20s isn't what your 40-year-old self finds appealing—and with a world full of beautiful cultures, natural wonders, and historical sites, things can quickly become overwhelming. Do you book that ski trip to Japan or save up for an excursion through the Galápagos Islands instead? To get the ball rolling, we've curated some incredible experiences for every decade of your life.…