I kept my sites up until I spotted the regular (not the fresh bot) Googlebot in the logs... Seemed to have worked out fine. It was about two weeks for the bot to show up but I'm sure it varies depending on the time of the month/crawl.
[edited by: lazyz at 4:42 pm (utc) on April 3, 2003]
4:42 pm on Apr 3, 2003 (gmt 0)
I would wait until your logs show googlebot visiting the new pages, however long that takes.
<edit>lazyz got there one full minute before me</edit>