How to prevent multiple carts

Hello, i had to put a long expiration (in days) for the cart becouse in my setup days can pass from the user to be activated by a moderator and the actual payment of the subscription. But sometimes it happens that the user logout and login multiple times before the payment or (i guess) exit and re-enter the payment form so multiple carts for the user are created and only the last one is actually going through the payment process.
Due to the long expiration of the cart in the "cart section" of the backend i have multiple abandoned carts of the same users. Is there a way to prevent this? Like if a cart for user "A" is created and already exists old carts that are not completed they are automatically removed?
I have 3 plans that are exclusives and users can't upgrade so i don't mind if old empty carts are removed (i still need the "completed" and "payed" old carts though).
Thanks
Gianluca

There shouldn't be multiple baskets. Their existing basket should just be reused. Are you sure new baskets are being created in CBSubs > Baskets? Regardless it shouldn't do any harm as those old baskets will eventually expire.