These weights are invented to demonstrate the calculation and are not recommendations.
Half-life: 30 days. Weights: reply to an email 20, meeting attended 30, pricing page viewed 5.
A contact replied to an email 10 days ago. Decay factor = 0.5 raised to (10 ÷ 30) = 0.79, so the contribution is 20 × 0.79 = 15.8.
They attended a meeting 45 days ago. Decay factor = 0.5 raised to (45 ÷ 30) = 0.35, so the contribution is 30 × 0.35 = 10.5.
They viewed the pricing page twice, 5 days ago and 60 days ago. Decay factors are 0.89 and 0.25, giving 4.5 and 1.3.
Total engagement score = 15.8 + 10.5 + 4.5 + 1.3 = 32.1. The meeting was the most significant single interaction by weight, yet the recent reply now contributes more, which is exactly the behaviour decay is there to produce. Note also that the denominator in each decay calculation is the half-life, not the observation window, so extending how far back you look does not change what recent activity is worth.