The update is instant, there is no refresh at all. What asterisk version are you using? I recommend to setup the asterisk manager as described in this blog post, but is good only for recent asterisk versions:
http://www.fop2.com/blog/make-fop2-snap ... ventfilter
An improperly configured asterisk manager can lead to disconnections and improper states on the panel itself.
Regarding the trunks, you will see activity if the trunk channel name in the button configuration matches the channel name that asterisk reports. You are not saying what kind of trunk are you using.. is it DAHDI? SIP? IAX2?
If its DAHDI, you must configure the channel number range in the fop2 buttons page in freepbx fop2admin, like 1-30.
If its SIP, more often than not trunks are incorrectly configured, or have two different peers to differentiate inbound from outbound. The default channel name that is picked by fop2 (as is that the one it is setup in freepbx), is the outbound name. If inbound<>outbound, you will have to add the inbound device name in the channel field in the fop2 buttons page. Or you can configure your peers so both inbound/outbound matches just one peer.
And it is very important that you have a properly configured /etc/asterisk/manager.conf, because if you are missing events, not only trunks will act weird but all of the features in the panel will.
Best regards,