Not every live stream is followed by an after show. One of the more common reasons for the absence of an after show would be when Brian has to get up early the next morning to catch a flight or if Brian is broadcasting from a remote location. Technical issues have also been found to discourage after shows.
Some of BBLiveShow's most epic moments have happened during the after show. Since the after show is not recorded, people have had to have been watching live to witness them. On very rare occasions, such as the Black people aren't slaves in America song and hobo vagina, some of these moments have been captured by fans.
In the early days of NSFW, after shows were less likely due to the necessity of having someone at the TWiT Cottage on TWiT's end of the broadcast. Later, however, the NSFW after show was held via the BBLiveShow Ustream feed while still using the TWiT chat room. Recently, Brian has used his Justin.tv page to stream the aftershows, with the occasional show done by Justin alone. These have been dubbed NSFWAfterShow and BBLiveAfterShow by some fans. An NSFW Aftershow Feed page has been created on BBpedia to present the video feed and chat on the same page.