Hello,
I want to give my customers an 10%discount code but i would like to limit that to only 3 products each month. Doesnt matter if it is 3 products in 3 orders or in 1 order. What does matter is that it renews every month. So every new month is 3 new Products with the discount code. If they want a 4th product in a particular month then thats okay but i wont have the discount.
I have been trying with different apps and the automatic discount codes from shopify but so far no luck
hope someone here can help me 
Greetings
Currently with only native discount codes the problem is configurations trying this model applies the discount to the entire cart not the first set of products, unless you do some hijinks with the setting “APPLIES TO Specific products”.
Closest way to do this is by having a discount code with “Limit to one use per customer” enabled , or by using customer groups with customer tags that you manually manage to limit to 3 “usages” as orders are processed.
An alternative is using BuyXgetY with “Minimum quantity of items = 1” so “Customer gets - Quantity = 1-3” other items at the discount with “Set a maximum number of uses per order = 2” and “Limit to one use per customer = 2”
If existing discounts cannot deliver this function, this can somewhat be solved with scripting automation apps like usemechanic
Example premade tasks https://tasks.mechanic.dev/?tags=Discounts
https://tasks.mechanic.dev/activate-a-discount-when-iss-passes-overhead
https://tasks.mechanic.dev/generate-a-product-discount-when-a-voucher-product-is-purchased
Or creating custom orders from the cart and adjusting costs/discounts https://tasks.mechanic.dev/create-a-draft-order-from-the-cart
Another approach is a duplicated products like membership-esque scheme where the products themselves are marked down and the purchases is limited to 3 items at a time using order restriction apps, max qty apps, etc. That method often needs another solution to keep the inventory synchronized. Note there’s a sublogic in there where each customer could get their own inventory stock per product to limit purchasing.
A big caveat to note is there’s no guarantee that new accounts aren’t being created to continue to get more discounts. If there is contractual restrictions for this, or regulations ,this is a hard problem without ID verification.
Also see https://community.shopify.com/c/shopify-discussions/customer-cannot-reapply-same-discount-code-after-first-order/m-p/1233464