i have on mz WMT one page where i see all my links and then few where is still 0 even they have PR4. how is this possible?
It depends on the site traffic and google decides it. Google let you select 3 options to control the speed of website crawling. Please search for you keyword and go to the cache-link and see the date when it last crawled.
i notice it changes a couple times a week but it's not a complete update. i have links that were marked as bad that have been fixed for over a month or longer and it hasn't updated them, others were nabbed almost instantly. It's definitely based on a lot of factors. Site size, site updates, link importance, etc.
I would say it depends on the section within webmaster tools. Most sections seem to update daily (Diagnostics, Statistics, etc). But for me the Links section has taken over two months for an update. I have a website that developed Google sitelinks about two months ago, yet my webmaster tools still says "Google has not generated any sitelinks for your site".