Wait, I think (all) web sites are crawled in 5 minutes. Because I created my site 1 week ago. But they crawl every five minute. Even without pinging they check it. I think Google improved its system in this months.
Google updates SERPs very very frequently!! 24/7 it looks for fresh content to index it on top..tons of algorithms works randomly to index the results!
Google updates SERP many times every week. Some times I have seend SERP updation quite a lot of time in 1 day.