Set lease time to 3 days

config/matrix-kea-dhcp4.conf

 {
     "Dhcp4": {
-        # Set the lease time to infinite
-        "valid-lifetime": -1,
+        # Set the lease time to 3 days
+        "valid-lifetime": 4320,
 
         # Next we setup the interfaces to be used by the server.
         "interfaces-config": {