Feedback on exit popup implementation

I have an exit popup. Currently the way I have it setup is if someone leaves and they have $X amount in their cart a popup shows with a coupon that can only be used immediately (the coupon is encrypted in a link to the checkout so they can't easily copy it and use it at any other time and they wont see the code). If they close out the window the opportunity wont show again for X amount of days or unless they clear their cookies. I was wondering if I should instead always offer the exit popup until they actually utilize the coupon. I personally hate seeing the same popup even if it's beneficial...but just in case I'm in the minority, thoughts?

Hi,
Maybe it could be like that :
- First time you display the popup coupon
- Next times no popup but instead you show a button to apply for the coupon during the checkout process
if so customer won't get annoyed by recurrent popup but still will be happy to keep the opportunity of the coupon !