Mage:: Init require more time to load

We are developing an website , by consuming the all the data using REST API in magento website. In that for session initialization , we are using the below code ,
$websiteId = Mage::app()->getWebsite()->getId();
Mage::init($websiteId, 'website');
Mage::getSingleton('core/session', array('name' => 'frontend'));
$session = Mage::getSingleton('customer/session', array("name"=>"frontend"));
$session->start();

If Mage::init is not initialized, we cannot able to set/get the session details. In every web services, while executing Mage::init taking 25-30 secs for each services.

could you please let me know , what is the another way to initialize in global and avoid initializing in individual service.

awaiting for your valuable reply