Magento – Magento: Limit Product Max Quantity Per Customer (NOT per Order)

I want to limit the product max qty per customer to only 1.

Example: If you buy the product my_product_per_customer as a registered customer you can not buy again with the same account.

Does anyone know a way to achieve this?

My config.xml is

  <?xml version="1.0" encoding="UTF-8"?>
<config>
<modules>
<Inchoo_MaxOrderAmount>
<version>0.0.2</version>
</Inchoo_MaxOrderAmount>
</modules>
    <frontend>
        <events>
            <sales_quote_save_before>
                <observers>
                    <inchoo_maxorderamount_enforceSingleOrderLimit>
                        <class>inchoo_maxorderamount/observer</class>
                        <method>enforceSingleOrderLimit</method>
                    </inchoo_maxorderamount_enforceSingleOrderLimit>
                </observers>
            </sales_quote_save_before>
        </events>
    </frontend>
</config>

My observer.php is

<?php 
class Inchoo_MaxOrderAmount_Model_Observer
{
    private $_helper;
    public function __construct()
    {
        $this->_helper = Mage::helper('inchoo_maxorderamount');
    }
    /**
     * No single order can be placed over the amount of X
     */
    public function enforceSingleOrderLimit($observer)
    {
        if (!$this->_helper->isModuleEnabled()) {
            return;
        }
        echo 1; die;
        //todo - look up customer info and check if they already purchase this item
        $quote = $observer->getEvent()->getQuote();
        if ($quote->getCart()->getItemsCount() == 1) {

            Mage::getSingleton('checkout/session')->addError('limit only one product per order');
            Mage::app()->getFrontController()->getResponse()->setRedirect(Mage::getUrl('checkout/cart'));
            Mage::app()->getResponse()->sendResponse();
            exit;
        }
    }
}