I've noticed on many directories that they are only cached once a month or less. Does this mean that they are only being spidered once a month hence not picking up newly listed domains? The reason this may be a problem is when submitting to a subpage of a directory as a sponsored listing on a monthly basis, you aren't getting any benefit for over a month. I know this may seem ridiculous, but when you pay for something should you not receive the benefit within a weeks time?
google will re-cache a page when it decides there is a lot more new content there. So if 1 word changes, it wont re-index it. If you add 1 new paragraph it probably will. So if category pages do not change much, they will not get indexed much
on most directories specially which are very active, google cache it much faster than one months time! about the benifits! i think directories have there own traffic so the benefit starts from the time the listing is approved,