Using Premiere Elements 9
My movie to all intentions purposes is just over 23 mins long.
However when I go to Share to make an MPEG from it the duration stated there is much longer i.e. 29 mins 57 secs.
If I click the checkbox 'Share Work Area bar only' the correct length is stated.
I don't understand what leads to the longer time when I don't tick the checkbox.
You probably have a few extra frames of video floating out beyond your movie.
Press the \ key (above Enter) to show your whole timeline. Then click and drag the area beyond your movie to snag any stray video and then delete it.