If you add an AirPort Extreme to your existing Frontier Net network and permanently connect the AirPort Extreme to the Frontier wireless router using a wired Ethernet cable connection...
AND......you locate the AirPort Extreme in another part of your house where you need more wireless signal strength and coverage.......
AND......you configure the AirPort Extreme to create a wireless network that uses the exact same wireless network name and password as the Frontier wireless network.......
Then, you will have a much "bigger" wireless network with much greater range with higher wireless speeds throughout the house.
That would be be a good investment if your goal is to have a much bigger wireless network with greater range and speed throughout the house.