For a few of the servers I admin, I found the need for the ability to add IP addresses to a pf table temporarily (for a few days, a couple weeks, etc).
I grew tired of manually editing the files, so I wrote a scipt to help me. The script maintains a list of IP addresses for a pf table, along with an "expiration date" for the address. Each night cron runs the expire portion of the script and the expired addresses are removed from the table. So far, it's been working well for my needs for well over a year. I decided to clean the script up a bit, put a BSD license on it, and make it available for anyone else who may want to use it. It's available here, along with a better description of what it does: http://archive.mgm51.com/sources/pft.html