Zen Cart Frequency Discounts

Zen Cart Frequency Discounts provides the ability to discount based on the current purchase and past purchases - either for all time or with a cutoff date specified in days, weeks or months.

Configuration parameters are as follows: 

1. Up to five admin specified purchase levels, and percent off discounts for each level.
2. A lookback period, defined in days, weeks or months (or without limit) that specifies how far back to go when computing the current spending level.

The customer's current spending level is computed by adding the total value of the products in the cart to either the total value of all products purchased within the configured timeframe, or the sum of all order totals within that timeframe. For instance, if the orders during the specified period were as follows:

Order 1:
10x Product 1:        $100
Sub-Total:            $100
Quantity Discount:    -$10
Shipping:               $5
Tax:                   $10 
Total:                $105 

Order 2:
1x  Product 2:         $90
1x  Product 3:         $10
Sub-Total:            $100
Shipping:               $5
Tax:                   $10 
Total:                $115 

If "Compute past spending" is set to "Order Total," the value would be $220 ($105+$115). If "Compute past spending" is set to "Product Total," the value would be $200 ($100+$100).