i have gone through most of the documentation about the sitemap XML. i could not figure out how often does Google picks up the sitemap XML. The contents on my website is always changing say every 1 hr, and if i want to list a page which contains a dynamically picked item from my DB. how would i do it..because every time a temporaory complete URL will be generated for this item which may no longer be useful in anohter 5 or 6 hrs.
i'll appreciate any help, as i am new to Sitemap fundamental