If the original post was too verbose, its basically this:
tcpdump captures in 30 (or xxx) minute chunks, in my case I store 3 days worth.
I then use sngrep to open the pcap and then search within to find the call or calls I am after.
I know what the calls I am looking for are because I look in fusion and find some call examples if the customer doesn't have any on hand.
A cron job deletes all files older than xxx days, minutes, hours or whatever.
These run all the time. There is no shipping the packets elsewhere, which doubles bandwidth consumption. Baring sngrep misbehaving this is fast and efficient.