This has always bothered me. In Quantum Leap, the string theory they explain in the show suggests that one can travel to random points in time within their own lifetime.
The Quantum Leap project exists in 1999, and episodes involve leaps to times before 1999, but why not anything after 1999?
I know the premise of the show was to fix something that went wrong in the past, but could there future events that need fixing too? You would think that Sam Beckett would be alive beyond 1999. I would like to think that this would make an interesting episode where he leaps into someone who exists in the future. Al finds him and they have no clue who Sam leaped into or what needs to be fixed. They would need to figure out what will go wrong to fix it. Their computer, Ziggy, is wrong most of the time anyways.