The old Traveller 'Mercenary' and 'High Guard' books. They had a unique character generation system that was like a lot like the game 'Life': you started out at 18 years of age, made career and education choices, and rolled dice to figure out if you suceeded. Would you start out as a conscripted foot soldier or a space academy educated star pilot? Your choices and the die rolls determined the outcome.
Then each year of your career was documented, with possible special assignments, skill improvements, medals or even death. You could opt out at any time and begin your adventuring career. Opting out early mean you were young but had little accumulated wealth or skills. Opting out later meant more risk of dying or loss of health due to age, but more skills and wealth, including the possibility of getting your own starship!