Hi hotbeehoney ,
Thanks for you post.
You can continue using the plugin forever after the license expiration. However, you won't be able to access our premium support and won't have access to plugin updates anymore. We periodically update our plugins to fix some bugs that may be found and to add new functionalities. Also, as time goes by, new versions of ATUM and WooCommerce may be incompatible with your outdated version of Multi-Inventory and stop working (though it will continue working if you don't update such plugins).
You can move your license up to two times. Also, you can create as many staging/development sites as you want. Their URLs only need to follow the rules you can find here.
Best Regards,
José Andrés