Instead of running ping you might just want to set the parameters in your ssh client to keep the connection alive.

Putty:

Under Connection
Seconds between Keepalives = 4
Enable TCP keepalives = checked

WinSCP:
Under Connection
Sending of Null SSH packets = checked
Seconds between keepalives = 4

OpenSSh Client:
check this link http://www.openbsd.org/cgi-bin/man.cgi?query=ssh_config


Other ssh clients should have similar settings. So far these have worked great for me.

Pete B