I'm 35 weeks and have not packed anything or even started organizing her things lol. But then again I am the biggest procrastinator I know and don't recomend doing what I do lol
The sooner the better you can start one and just add to it
I was told to pack it around 38 wks but since I was early with my first I was packing it after my water broke that morning. luckily I had stuff picked out ready to be packed.