Heyday youth refers to the period of someone's life when they are at their prime and experiencing their greatest success. There are many synonyms for this phrase, including peak years, prime of life, golden age, high point, and zenith. These terms all evoke the same idea of someone at the height of their abilities and enjoying the best years of their life. Other related terms include the phrase "youthful vigor," which highlights the energy and vitality that accompanies this stage of life. No matter which term is used, the idea of heyday youth is one that many people aspire to and work hard to achieve.