Clients who've endured conversations with me about their recommended asset allocation know how much I stress the importance of their investment time horizon. During a recent discussion about investment ideas, my dad suggested "What's your time horizon?" be my epitaph. Maybe so, but considering in advance when you will need the money you're investing can keep you from making the worst kinds of financial mistakes. And keeping your investment horizon in mind during periods of market turbulence should help keep you on course for attaining your financial goals.