One sitemap file can hold up to 50,000 URLs, so large listing sites split theirs into several files. The last-modified dates should change only when the page really changes; a sitemap that marks everything as updated today is easy for search engines to learn to ignore.
Why it matters to an agent
New listings get found sooner when they appear in an accurate sitemap the day they go live.
How ListingHQ handles it: Website & Listings →