source Ruckus KB article:
"Once a client makes a connection, AP will keep monitoring for its
traffic. If there is no traffic at all for a certain period of time, the
AP will remove that particular client's entry. This period is called
Inactivity Timeout. The default value is 5 minutes and it can be raised
all the way to 500 minutes. When this value gets triggered, AP will also
send a disassociate packet to the client and log a message under
events.
This type of purging of inactive client entries is
essential especially if the environment is highly transient in terms of
client foot traffic. This is true for shopping malls and city-wide WiFi
deployments. This purging will avoid ZD side resource consumption in
maintaining client entries that are no longer active on the network.
This will also help to avoid ZD reaching system limits in terms of
number of clients that can connect.
There may be certain
deployments where 5 minute default inactivity timeout can cause
unnecessary client disconnection. Examples include warehouses that use
barcode scanners. Barcode scanners can be silent (non-chatty) to
conserve battery power and communicate only if required. In these
conditions, if the scanner gets disconnected, it has to reconnect back
which will be unacceptable. For such SSIDs, raising inactivity timeout
value is suggested".