Google's DNS cache

How often does it update now?

[Umbra]

An old thread stated that Google updates it's DNS cache about once a month. However, that was the old reliable Google.

Through all the recent ups-and-downs, how often has the "new" Google been updating its DNS caches?

I ask because one of our webhosts will be moving domains to a new server (and hence, new IP addresses). I know that a copy of the site should remain on the old server, until Google updates its DNS cache and starts spidering the new IP address. However, our webhost maintains that it's too expensive to keep the old servers running after the move.

Our index page has already been infected with the strange disappearing virus that's been going around. I would like to prevent an IP address change from causing further damage.