Mine was ready for about 6 weeks before my due date, then he was 8 days late! And i didn't actually touch it during my labour as it was so quick, and ended up staying in hosp for 8 days so hubby still had to bring me stuff in!
Couple of tips for first timers though - disposable pants are pointless! Get some BIG cheap pants, i had to get my mum to buy me some as i had an emergency section and the pants i had which i though were big sat right on my scar. Also, if you're planning on breastfeeding, Lansinoh is the only nipple cream worth using, cheap ones are pointless, but Lansinoh was a lifesaver! And bear in mind that labour and postnatal wards are like saunas!