When Dana Saperstein quit her marketing job to spend six months hiking the Pacific Crest Trail, the then-31-year-old thought of it as a microretirement. “If I keep working myself to the bone until 60 years old, I might physically never be able” to hike the 2,650-mile Mexico-to-Canada trail, she said. Saperstein is among a small number of workers in their 20s and 30s borrowing years of freedom from their future selves to enjoy some of their retirement while they are still young.