What to do with an outsourced airport extreme base station 5th generation?

If you have kids or frequent guests and would like to set up a separate WiFi network for them to use......so you don't have to provide them with the password for your "private" network.......the AirPort Extreme is up to the task.

The AirPort Extreme could also be used to provide extended coverage for your current WiFi network if there is an area of the home that needs a stronger signal. That's the upside. The downside is that the AirPort Extreme will need to connect back to your main WiFi router using a permanent wired Ethernet cable connection.

As long as it is still functional, there shouldn't be any reason not to keep it as a spare. Other options would be to give it away to a friend or relative ... or, even, provide it to your favorite local charity that, in turn, can offer it to others in need.