POIs change more rapidly than roads, for the most part, but HERE isn't always trailblazing in that area either. We have a few road changes nearby, and it drove my wife nuts to be "offroad" in her new car, so we got an update ASAP ( meaning more than a year after the 2014 was purchased... ). On our other Alpine/Acura Nav system, we typically do updates every few years. Mostly so my teenage driver will keep his damn cell phone in his pocket when he is driving.
As for firmware updates, documentation of changes? That gave me the giggles. Not. And there seem to have been stealth hardware changes, so the applicable firmware versions are tied to a VIN range, and VIN is required when you order an update. Looks like they want to know "device ID" and current map database revision numbers too. This lends credence to the claim that the update is tied to a particular vehicle. And yes, our 2014 is an orphan for some software/hardware improvements in subsequent model years. So the basic concept is WYSIWYG. Don't expect meaningful improvements after purchase, aside from ( maybe ) stomping out major bugs.
There used to be a tool on the old Navteq site to preview the maps and see if they were up-to-date in areas of interest, but I can't find anything like that anymore.