whenever you want. we moved when i was 34 weeks, so i obviously had to wait. we had all the stuff though, so if we hadn't been moving i would have set it up much sooner.
then i would go in every day and swoon and look around.
then i wanted to cry when i went in when i was overdue. i was a tad emotional and i felt like i would never have a baby to occupy the cute nursery.