I recall soon after the oil spill he published a comic directly on his blog, stating that if he published it through the normal route, it would take upwards of 2 months to get through the process, and would no longer be relevant. I'll post the link if I can find it.

edit: My bad, it was the iPhone 4 prototype debacle! But he directly answers the question about how far he works ahead. http://www.dilbert.com/blog/entry/thatlost4gphone/