Roger Federer is one of the most successful tennis players of all time and is still competing at the highest level of the sport at the age of 38. His longevity in the sport is largely due to his exceptional physical fitness, tactical awareness, and dedication to the sport. He has also been careful to manage his body and avoid injuries throughout his career, with regular breaks and a tailored training schedule. His mental strength and passion for the game has also been a major contributing factor to his longevity in tennis. Overall, Federer's incredible combination of physical, tactical and mental strengths, as well as his dedication to the sport, has made him one of the most successful and longest-lasting tennis players of all time.