I ran into the overflow behaviour with our source repository provider, as they'd get hammered on the top of every minute by all the continuous integration servers and silently drop connections. The specific version of SSH we were running didn't send the client banner until it received the server banner, so the connection just hung for 2 hours on the client.

After much debugging and reading of kernel source this was all figured out, and the provider adjusted things on their end so this wouldn't happen.

Moral of the story: You probably should set tcp_abort_on_overflow to 1.