Since switching to Xfce, I get notifications in the pannel/system tray about available package updates via pk-update-icon. It buggered me for a while because I found it was popping too often. The man page is clear about how to adjust the interval (use -i; the default is 2 hours), but since the program is started automatically I didn't know where to put that option in.
`rpm -ql pk-update-icon` indicates that the package installs '/etc/xdg/autostart/pk-update-icon.desktop' and sure enough that is the file to be edited; append desired options to the Exec= line. Now how would that be done per-user or without super-user privileges?