How long for page to move up

Hi - I was wondering does anyone is there a waiting period after a page has been adjusted (i.e. metatags and content) after Google has picked up the changes for that pages ranking to increase.

I can see that a couple of sites where I made changes, that Google has picked up the changes but the sites ranking has not been affected at all.

In comparing the top 5 pages for these terms and comparing my sites, my sites have the same number or more of back links, better metatags, more content reflecting the key words, higher PR, ODP link, etc. Seems strange that the top sites for the same key words many times do not meet the same criteria but remain at a higher ranking.

There must be something I am missing or does it just take some time for Google to make adjustments to the listings after changes have been made? -Beth