Signal half-life matters as much as signal direction. Mechanism: A signal that points the right way but decays quickly should not be traded with the same holding period as a slow structural signal. Time is part of the thesis. If the horizon changes, the execution logic should change with it. 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. $$ Signal\ Value_t = Signal_0 \cdot e^{-\lambda t} $$ Plain English: Some signals lose explanatory power quickly, so old information should get less weight. Failure mode: The expensive error is mixing a fast entry logic with a slow stop and calling the result "conviction." Review question: Write down the state variable you would monitor first if this thesis started to drift. That is usually where the edge is: not in the vocabulary, but in the structure underneath it.