handshake

I have quite a few smartdevices, and every 55 minutes I get a raft of: WPA: group key handshake completed (RSN). I assume this is actually a good thing, but I would like to increase the time between handshakes, but I can't find the setting. Help, anyone?

Is there a browser configuration that needs to be made when you configure Asuswrt-Merlin (currently 384.4_beta3) to be accessible via https://<router's ipaddress>:8443 ? Using Firefox 58.x and 59.0, the browser displays the following and eventually times out.