Google posted a new Webmaster Help video today. This time, Matt Cutts addresses a question posed by fellow Googler John Mueller, who asks:
A newspaper company wants to add an archive with 200,000 pages. Should they add it all at once or in steps?
Cutts says, "I think we can handle it either way, so we should be able to process it, but if we see a lot of pages or a lot of things ranking on a site all of a sudden, then we might take a look at it from the manual web spam team. So if it doesn't make any difference whatsoever to you in terms of the timing of the roll-out, I might stage it a little bit, and do it in steps. That way, it's not as if you've suddenly dropped five million pages on the web, and it's relatively rare to be able to drop hundreds of thousands of pages on the web, and have them be really high quality."
"An archive of a newspaper is a great example of that," he adds. "But, if it's all the same to you, and it doesn't make that much of a difference, I might tend to do it more in stages, and do more of a gradual roll-out. You could still roll them out in large blocks, but you know, just break that up a little bit."
So it doesn't sound like you're going to have any major problems if you do it all at once (provided you're not actually spamming Google with low quality content), but you might be raising a red flag with the web spam team, so it's probably better to err on the side of caution, as Cutts suggests.