Data update frequency on major search engines

This is a report on frequency of leading search engines’ data update. 
I’m maintenancing my company’s official web site and  I had a chance to completely renew it  recently. 
Our web site had a definite defect before:  It is made as static html files which are created by Microsoft’s Front Page, so if we want to add some contents, it can affect many (some times all)  pages and it is very difficult to maintenance.
Therefore I decided to make use of Content Management System and tried to make it very simple.   I cusomized a CMS which utilizes database and php, take over some contents from the old web site, created some new contents and finally published them to the Internet.
I’m curious about how many days it will take for search engines to update their data.  After I replaced the contents,  I frequently checked some search englines if the new contents can be searchable.  The result is as bellow:
Yahoo!: 1day
Mooter: 1day
Google: 5days
MSN: over 7days
-Yahoo! is the one on which I could find our latest contents first.
-Google bots come our web site most frequently, but it is comparatively slow reflecting their data.
-It seems that the top page is collected and reflected first and other pages are reflected at a later time.
-Old contents still remains in search results.