I read a great book a long time ago.. wish I could remember the name.

Basically, sometime in the future, Earth is dying, so everyone has to leave to some faraway planet within 100 years.

The first intrepid explorers leave at T-100 years, expecting to be the first to arrive. A few years later a new craft leaves that can travel faster and will get there sooner. This goes on and on until it comes down to a betting game of how late can you wait until leaving, while still being the first to arrive (and thus claim ownership/leadership, etc.), with people coming up with all kinds of hair-brained schemes on the best time to actual leave.

IIRC, it kind of turned a little into Hitchhikers Guide kind of ridiculous near the end.