How about this?
$em = $this->getDoctrine()->getManager();
/** @var $repo MyFirstEntityRepository */
$repo1 = $em->getRepository('MyNamespaceMyBundle:MyFirstEntity');
/** @var $repo MySecondEntityRepository */
$repo2 = $em->getRepository('MyNamespaceMyBundle:MySecondEntity');
/** @var $repo MyThirdEntityRepository */
$repo3 = $em->getRepository('MyNamespaceMyBundle:MyThirdEntity');
Seems to me declaring variable $em
solves all the DRY violations...