Folks! I have found the setting in the putty SSH client which enables the client to send a null packet to the server daemon process ever 'x' seconds. Hmmm... Big sigh of relief for me!! It was driving me crazy..
This is what you have to do to keep the SSH / Telnet connection alive for extended period of time.
Open putty settings, navigate to SSH, There will be an option to give the keep the connection alive. By default it will be '0', change it to something between 5 to 30.
Then save the settings to the default setting, so that this setting will be made permanent.