This is the same feature in Salla stores,
If you use one coupon code, you can't use another (same or different) in the following months.
This means a merchant is allowed to get a discount only once.
Currently, if coupons are activated, one merchant can use multiple codes, applying different coupons each month.
Which makes it:
A) Not ideal since if there is a discount, the merchant will get a discount each month.
B) Not useable if we want to create affiliate partnerships since the tracking will be hard.