I recommend "Chicken Dinner: 80 Years Old before Activating the System" to you! In this novel written by the author, Jiu Yan, the protagonist not only became an 80-year-old man after transmigrating, but he also obtained a rejuvenation system. The main character could kill other players in the game and obtain money and skills. What was even more amazing was that he could recover his age. This novel fits the information you gave. There's a more direct way than exchanging age for experience! I hope you like this fairy's recommendation. Muah ~😗