Threshold for PPPoE AC is somewhere near to 1.4k active connections. More active client connections make mess. It is problem on ccr1036 or ccr1072. It doesnt matter. I even turned off NAT, Connection tracking and firewall. For this i have separate ccr 1072. Only using simple queue and pppoe and it drops active clients and makes tunnels without router, so it create problem for client to get connection when reaching 1.4k connections.
Now i am running 3 PPPoE AC /2 in production and 1 as backup/. I mirror secrets by script.