Google’s John Mueller was asked in a video hangout on Google+ this morning if priority and change frequency matter much in XML Sitemaps and John from Google said nope.

The question was asked at the 29:35 mark:

John answered:

This is essentially the advice Google gave when going mobile friendly, to update your Sitemap file with the time stamp of the date/time the site went mobile friendly, so Google can pick up on those changes faster.

Here is the video embed at the start time:

Forum discussion at Google+.