I found this link that explained how to set maximum time for ALL calls or just OUTBOUND calls using FreePBX.
Thanks to this link/user: http://www.trixbox.org/forums/trixbox-forums/help/how-do-i-limit-call-length-or-call-duration/eihoward
Go to FreePBX General Setting.
You will find two Dialing Options:
To set limits on ALL calls, modify the “Asterisk Dial…” box, to set time limit for Outbound calls, modify the “Asterisk Outbound Dial…”
Here in my server/example, I am setting limit to 4 hours max and 3.9 hours to warning message before hanging up a call (forcefully).
The values are
Where L denotes the function Limit and the first value is for the max time and the second is the warning time in milliseconds (1 sec=1000 ms)
In the case above, I am only wishing to limit Outbound calls to 4 hours MAX.