Thanks! The -B parameter works to limit recording time.
If it helps someone in the future, this is how I have my setup:
1. Windows Task Scheduler runs a task for whenever my favorite NRB show airs. The task runs this VBS file.
Code:
Dim WinScriptHost
Set WinScriptHost = CreateObject("WScript.Shell")
WinScriptHost.Run Chr(34) & "C:\record NRB.bat" & Chr(34), 0
Set WinScriptHost = Nothing
2. The VBS runs this BAT file ("record NRB.bat"), which runs rtmpdump.exe. (Running the BAT from the VBS allows it to run invisibly, rather than in a console window.) The fancy code in the filename is just the current timestamp. For example: myfavoriteshow_2014-07-30_14-38.flv.
Code:
"C:\rtmpdump.exe" -r "rtmp://imavex.fc.llnwd.net/imavexpush" -a "imavexpush" -f "WIN 13,0,0,214" -W "http://www.streamotor.com/player/mediaplayer-5.10-licensed/player.swf" -p "http://nrbnetwork.tv/Pages/watch_online.aspx" -y "universal11" -o "C:\NRB recordings\myfavoriteshow_%date:~10%-%date:~4,2%-%date:~7,2%_%time:~0,2%-%time:~3,2%.flv" -B 1800 -v
3. rtmpdump.exe is now running invisibly. The "-B 1800" section of the above code means that rtmpdump.exe will stop recording and will close after 1,800 seconds (30 minutes).
You can set Windows Task Scheduler to do this once a week, or whenever the show airs. If you missed an episode, just look in your NRB record folder!