Yes bruteforcing a router can take forever. The average time depends on the fast the router is, how much ram it has, and how fast it can accept a connection. I once had to allow public access to some Cisco 2600 series routers, so I put them behind a iptables firewall. In the iptables firewall I added a rule that only 3 connections could be made in 5 minutes. Check out --limit in iptables for more information on that. So this would really slow down any bruteforce attack, but it also can cause a DOS to legit users. You have to balance security and inconvenience to users.
Using hydra without understanding it and the equipment you are using it on can cause all sorts of problems for the equipment. I had routers lockup solid, drop packets, just act plain crazy.



