I start making my check list and gathering stuff together about a week ahead of time. That way I have the time to run out and get the last minute stuff I need.
However, I don't actually put anything into my suitcase and laptop bag until the night before I leave.
Actually, I even do some of my packing (beauty products, medication, iPod, etc) right before I leave for the airport.
My mother on the other hand, told me today that she is packing her suitcases tomorrow. We don't leave for 8 days.
That's going to give her cat a lot of time to lay on top of the suitcase and scream at us.