1. Time Until Payback is a critical metric for evaluating investments, focusing on how long it takes to recoup the initial investment through earnings. 2. MercadoLibre's TUP is estimated at 12 years, making it relatively attractive compared to the S&P 500's 14-15 years. 3. Fast-growth stocks like MELI offer significant upside potential but come with higher volatility and a wider range of outcomes; patience and long-term holding are key.