http://stackoverflow.com/questions/13584054/magento-abandoned-cart-for-guest-unconfirmed-users
SELECT entity_id, customer_firstname, customer_email, items_count, grand_total, created_at
FROM sales_flat_quote
WHERE entity_id NOT IN (SELECT quote_item_id AS quote_id FROM sales_flat_order_item)
AND items_count >0
AND customer_email IS NOT NULL
ORDER BY `sales_flat_quote`.`created_at` DESC
http://stackoverflow.com/questions/15148275/when-does-magento-consider-a-cart-to-be-abandoned-wheres-that-time-limit-set
As you probably know the setting is located here:Admin => system => Configuration => Sales => Checkout => Quote Lifetime (days)This will add the setting to the database (core_config_data table) with path:checkout/cart/delete_quote_afterThis path is used in the code on:app/code/core/Mage/Sales/Model/Observer.php line 54So when someone is adding something to a cart it will be updated. When a customer logs in and his cart is there it will be updated. When a cart is not updated for the last 30 days. It will be removed.Extra information:In case you wonder when this code is used, It is used by the cronjob of magento.check: App/code/core/Mage/Sales/etc/config.xml line 1732
0 0 * * *
Hope this helps.