The flaw with this logic is that growth stocks and alternative assets such as cryptocurrency often have pronounced volatility when compared to more mature or mainstream opportunities. From there, we'll break down the composition of an ideal retirement portfolio and assess Bitcoin's (BTC 0.88%) role within this broader structure. How much money do you need to retire? This simply means that retirees can withdraw 4% of their portfolio's value per year for spending needs. If you want to retire by the age of 35, you'll need some big gainers in your portfolio and holdings that provide you with buying power for decades.