Thanks for trying out Premiere Rush and highlighting your doubt.
Premiere Rush free starter plan gives access to all the features of the app but limits export count to 3. Currently, this is a lifetime limit. Though Rush trial won't expire ever i.e. one will always be able to use all functionality of the app.
Moreover, Premiere Rush is available by default with Premiere Pro subscription. If you have Premiere Pro subscribed, you will be able to export countless times in Premiere Rush.
You can also submit feature requests for anything you would like to see in Rush here : Premiere Rush: Hot (410 ideas) – Adobe video & audio apps
Keep raising your concerns. !
We are continuously working to provide the best experience to our users.
Glad to help,