When you strip the noise away, the real question is simple: signal half-life matters as much as signal direction. Three quick checks before you act: 1. Name the mechanism in plain English: A signal that points the right way but decays quickly should not be traded with the same holding period as a slow structural signal. 2. Say why it matters for behavior or portfolio decisions: Time is part of the thesis. If the horizon changes, the execution logic should change with it. 3. Set the review question: Write down the state variable you would monitor first if this thesis started to drift. Market translation: A short-horizon mean reversion signal on $QQQ is a different object from a medium-term trend-following process on the same ETF. Failure mode: The expensive error is mixing a fast entry logic with a slow stop and calling the result "conviction." $$ Signal\ Value_t = Signal_0 \cdot e^{-\lambda t} $$ Plain English: Some signals lose explanatory power quickly, so old information should get less weight. The point is not to memorize the label. The point is to know what variable is actually doing the work.