So another question, how often should I update the Kep files?
Keps for the ISS should be updated almost any time you want to work it or listen to it, as the ISS orbit changes over time (normally gets closer to the edge of the atmosphere, and occasional reboosts to raise the orbit). Other satellites don't need to have their keps updated as often, but most tracking programs/apps can easily do that if the computer or mobile device has Internet access.