Remove quotes that belong to anonymous users with expired cookies (because they'll never be able to retrieve them)

gistfile1.aw

    /**
     * Clean expired quotes (cron process)
     *
     * @param Mage_Cron_Model_Schedule $schedule
     * @return Mage_Sales_Model_Observer
     */
    public function cleanExpiredQuotes($schedule)
    {
        Mage::dispatchEvent('clear_expired_quotes_before', array('sales_observer' => $this));
        
        $lifetimes = Mage::getConfig()->getStoresConfigByPath('checkout/cart/delete_quote_after');
        foreach ($lifetimes as $storeId=>$lifetime) {
            $lifetime *= 86400;

            /** @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */
            $quotes = Mage::getModel('sales/quote')->getCollection();
            
            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time() - $lifetime)));
            $quotes->addFieldToFilter('is_active', 0);

            foreach ($this->getExpireQuotesAdditionalFilterFields() as $field => $condition) {
                $quotes->addFieldToFilter($field, $condition);
            }

            $quotes->walk('delete');
        }
        
        $lifetimes = Mage::getConfig()->getStoresConfigByPath('web/cookie/cookie_lifetime');
        foreach ($lifetimes as $storeId=>$lifetime) {
                      
            /** @var $quotes Mage_Sales_Model_Mysql4_Quote_Collection */
            $quotes = Mage::getModel('sales/quote')->getCollection();
            
            $quotes->addFieldToFilter('store_id', $storeId);
            $quotes->addFieldToFilter('updated_at', array('to'=>date("Y-m-d", time() - $lifetime)));
            $quotes->addFieldToFilter('customer_id', array("null" => 'dummy'));
          
            foreach ($this->getExpireQuotesAdditionalFilterFields() as $field => $condition) {
                $quotes->addFieldToFilter($field, $condition);
            }

            $quotes->walk('delete');
        }
        
        return $this;
    }