This is one of those things that I have complained to EMM about but they do not seem to care; ideally, they should not only list the version number on their site with date but also the change history. At this point, the only way to determine whether there has been a new update is to call and ask or to download the zip file from the site, unzip it and look at the revision number of the file compared to the last file you downloaded.
The XDS1 is relatively new and so far the updates have been monthly but I expect this to taper off over time.