if you already have a script to determine when an add is posted, then unvoicing after some time is easy.
All you have to do is keep an hash that uses the voiced nicks as keys and the value is the last time that nick posted an add [use $ctime for this]. Then you could have a timer that periodicaly checks all entries in this hash to see if the difference between current time and the time in the hash is a number that would mean they're not serving anymore... in that case, devoice the dude.
hope you can script it from here
