Allow clients who have purchased a product with a time based update subscription access that ables the to download the product/software via a direct link without the need to login to their account.
Basically making use of the licensing add-on of WHMCS to validate the origin of the request that they in fact can download the product, automatically to update their software (watch this tutorial to understand more).
Like Wordpress and Joomla extensions can update via a click of a button on the client website without the need to go to the developers website. So extension developers like me would use the licensing add-on in their component to give users access to updates for the period of their subscription to my product (software) in WHMCS. Once the subscription stops they also no longer get automated updates access, but need to renew the subscription.