Which PuTTY keep-alive interval prevents NAT timeouts without triggering server-side security alerts?

PuTTY provides a mechanism under Connection > SSH to send null packets at specific intervals to maintain active sessions. This is primarily used to prevent firewalls or NAT gateways from dropping idle TCP connections.

While this client-driven behavior ensures session persistence, there is a tension between maintaining the connection and avoiding security triggers. Setting the interval too low may cause security appliances to flag the traffic as a denial-of-service attempt, while setting it too high may fail to prevent the timeout.

Does the interaction between PuTTY's keep-alive packets and the server's ClientAliveInterval create redundant traffic that impacts performance? What is the recommended interval to balance stability against security appliance sensitivity?