I was using yarpp_related( ... ) option in order to show the related posts for a custom post type. I realized that the items displayed were not going through the caching mechanism.
I could not find a clear/simple explanation elsewhere so I am posting the solution I came up with.
So, If you want to make the custom post types work with caching:
Add 'yarpp_support' => true to your functions.php
register_post_type('myCustomPostType', array( ........ ........ ........ 'yarpp_support' => true ));
Now you will see your custom post type name in the settings section -> "post types considered"
In your template file, use
<?php related_entries(); ?>