Google Cache Dates Not Updating

Checking the Google cache on numerous websites I found lots had the latest date from nearly month ago even one of the most recent ones – my Wheelchair Ramp website has a cache date of only 6th April.

I decided to set up a little test by adding a new line of text to a page, searched for the new line of text a couple of days later, and as expected, the page was appearing in the Google results.

On checking the cache though it was still showing the version before the line of text was added.

Is the Google Cache checker going to go the same way as the PageRank indicator?