For many 25-year-olds, becoming a millionaire sounds like something reserved for entrepreneurs, professional athletes, celebrities or people fortunate enough to invest in the next great technology company. But becoming a millionaire by age 55 may require something far less exciting: consistent investing, an average 8 percent annual return and 30 years of patience. The most valuable financial asset a 25-year-old possesses isn't money. It's time. Consider someone who begins at