User blog comment:UFO Editor/Season 8 Spoiler Topic/@comment-3411410-20110709145751/@comment-392210-20110709184811

I don't know about that, I kinda have a feeling that Preston and Porter were written off as regulars (well, Porter anyway) due to them moving out in 7.15. Notice how they were in only 1 out of the last 8 episodes of the season.