SOP: Apply EPC decay so yesterday matters more than last month

SOP: Apply EPC decay so yesterday matters more than last month
Straight 30-day EPC reacts too slowly; today's EPC is too noisy. Use a weighted decay.

— Step 1: Pull EPC for the last 1, 3, 7, and 30 days per offer.
— Step 2: Weight them: 1-day ×4, 3-day ×3, 7-day ×2, 30-day ×1.
— Step 3: Compute the blended score = sum(EPC × weight) ÷ sum(weights).
— Step 4: Set rotation weights proportional to the blended score, not raw EPC.
— Step 5: Require a minimum click volume per window before trusting it, or recent noise dominates.

This makes the rotation react to a declining offer in days, not weeks, without overreacting to one good morning.

Recompute the blended score on a fixed schedule — every day at the same hour for clean comparisons.

Run the decay calc daily.