What tells a triggered port to close

Hi all,
What tells a triggered port to close?
Just how long is it suppose to take to close the triggered port?
Just how long is a triggered port suppose to stay open after I close
the application that opened it.

After I close Yahoo Instant Messenger Webcam it has taken as much as
25min,98,13,50,85,78,16,43 for the Linksys BEFSR41V3 1.05 port
triggering to close port 5100. I would like it to close sooner for
security reasons.
I found this out by going to ShieldsUP and continually checking port
5100 untill I get a Passed and seeing the delay in time it takes from
when I close the Webcam to when port 5100 closes.
Are these random times normal? I would think the times should be
shorter and a fixed value each time.
Seeing the random times seems to tell me something else causes port
5100 to close such as maybe Yahoos server, which is hard for me to
swallow.
So why all the large random delay times?
Would someone else try this and see what kind of results you are
getting.
Thanks

Hey guys
I found out Yahoo Messenger video and voice work without even opening
ports on my router. I should of tried no ports open first just to see
what happens. I get a Stealth reading at ShieldsUp on ports 5000-5010
and 5100 while in a chat room.
You figure