A generic theme can occur at the end of the show because 1. A logo does not have it's own theme. 2. A generic theme might remove the logo's original fanfare for example: 20th Century Fox Television. 3. Fox wanted to introduce it's generic theme back in 1997, starting with the channel's 1997-1998 season debut.
CBS Monday Night 800pm - How I Met Your Mother 830pm - The Class 900pm - Two and a Half Men 930pm - The New Adventures of Old Christine 1000pm - CSI: Miami