
I think you are both right. High PR is gained through large numbers of backlinks and large numbers of backlinks results in more bot visits and faster reindexing.
And Robdale makes a good couple of points that content changes result in more bot visits and you can even tell the bots how often the page updates. Although I thought it was in the sitemap.xml file and not robots.txt e.g. <changefreq>daily</changefreq>