I wish I had a good answer for that. In speaking with a Google AdWords rep about this, all that I could divine was that if your ads are not running (i.e. if they are paused), then there will not be a re-scoring.

I could not get an answer to whether or not Google crawls the ads themselves, or if this is a backend process.

That same AdWords rep indicated that the experience we had with a re-scoring within a few hours was atypical.

For what it’s worth, here is Google’s standard answer that says “soon” but gives no direct time:

http://adwords.google.com/support/bin/answer.py?answer=49063

Here are excerpts from that link:

“AdWords visits and evaluates advertiser landing pages on a regular basis. If you’ve made significant changes to improve the relevance and quality of your landing pages, you should see higher Quality Scores and lower minimum CPC bids for your keywords. You will probably not see an impact within the first few days, but should see results over time.”

“We’re unable to guarantee a timeline for any improvement to your Quality Scores should you make any changes to your landing pages. If you don’t see lower minimum CPC bid requirements, you should evaluate our guidelines and verify that your changes are meaningful and substantial. Minimal or superficial landing page changes are unlikely to result in strong Quality Score improvements or lower costs.”

“Also, please be aware that some websites may always experience lower Quality Scores due to the nature of the site’s content. In these cases, such sites may be unable to further improve their existing Quality Scores.”

I have a question though…Does the bot visit everytime the ad is shown or when you update your landing page while having the campaign active?