If they were going to restrict coupon use, they'd tell you first. For instance, they'd return a message, "You've used too many coupons for this month, please try again later. While you wait, please give us your monies."
Usually you'll see a restriction in the Coupon E-mail about how it can be used, how many per time, etc. I doubt they'd ban someone over it if they used too many.
If they didn't give you a restriction, it's their loss for not being specific.