Are the 5000 coupons different in any way beyond coupon code? If not there's no real reason to create 5000 unique coupons. Instead it'd be best to use a single coupon that can be used 5000 times. I recommend the below to ensure it's only used once per user as well.

Maximum uses in total (0=unlimited): 5000
Maximum uses per customer (0=unlimited): 1

If you are still needing to create 5000 coupons I recommend first creating 1 then creating them directly in the database. Specifically see the _cbsubs_promotions table. Easiest approach is probably a CSV export using phpmyadmin then you can use any CSV editor to add new rows, etc..