tcp timeout in linux kernel

Some processes on our systems leave idle connections which get cut off by our external firewall after a certain amount of time as per its intentional configuration. We're attempting to fix this by modifying the tcp timeout directly in the linux kernel. My colleague believes that echo'ing a new value into:

/proc/sys/net/ipv4/tcp_keepalive_time

that is lower than the default of 7200 seconds and which correlates better with the firewall timeout will fix our problem. I'll be curious if it works.