One thing is that almost every leap has some personal significance for either Sam or Al, such as:
[ul][li]Leaping into younger versions of himself or Al.[/li][li]Visiting a log cabin in the woods, which he used to visit when he was a student[/li][li]leaping into a retarded man, who reminds Al of his dead sister[/li][li]leaping into a kid on holiday with his family - Sam took a similar trip at the same age[/li][li]leaping into someone who knows Al’s first wife.[/li][li]leaping into an actor in a time travel TV show, which he watched as a child, and which influenced him to research time travel.[/li][/ul]
and so on.