Automated push to PowerBI

I'm trying to implement a long-running job that will handle scheduled and automated pushing of data to PowerBI. I've gone over a bunch of examples and they all seem to require some sort of user intervention to log in and get an auth token to use with the REST API.

Is logging in once when the app starts enough or will someone have to keep logging in to get a new token when the old one expires? I'm looking to get this completely hands-off if I can, so if there's another way to periodically push data to PowerBI, please enlighten me.