WooCommerce Subscription - recurrent rewards
By default, if a user refers someone, he will receive a single coupon as a reward, but if you want to keep rewarding a user as long as a referral is renewing his subscription, you can do so by adding the below code to your functions.php file:
remove_filter( 'wcs_renewal_order_meta_query', 'gens_prevent_referral_copying', 10, 3 );
If you add this code, each time the referral pays the subscription, the user will receive a new coupon, which means that he will be receiving rewards as long as his referral is renewing.