Under the assumption that you're talking about the "We index it for you"
option, instead of a downloaded copy:
We update the index to each site once a week. We will host indexes up to
2500 pages, and a page may not exceed 25K. If you intent to go over these
limits we suggest you download the free Webinator for your site.
You'll know by seeing your Web log, the only message we send is if
your index has not been accessed recently and is being purged.
You can also see the time of last update by clicking on the
magnifying glass for a retrieved document. It shows the update time.
Thanks,
Thunderstone