I've found that if you want to quit LimeWire but don't want to disconnect from the people who are currently downloading files from you (and vice-versa), if you set the "Max # of Connections" under the Upload Prefs to "0", and then set your exit prefs to "Exit After Transfers Complete", LimeWire will refuse further upload requests, allow the people currently downloading from you to complete their downloads, minimize to the system tray (under Windows) and exit once all transfers (up/down) have completed. It's not the same as having a "Exit After Transfers Complete/Prevent Further Connections" option to quit LimeWire but it gets the job done.