My previous system was a Blaupunkt DX-R52, and they provide map updates every 6 months (at approx. 150 / CD, and a CD is one country)... I only bought one update over time, because it added the codes for TMC. It was about 3 versions after my original one, but it did know a lot of changes to the roads.
My father has a portable Blaupunkt, and the points of interest are very outdated (we could tell by the lists of pharamcies by name: there were names on it from pharmacies that were taken over 10 years before we bought this portable satnav!
).
So my take on it is that they will update the roads as much as they can, but not necessarily the POIs... I'd get an update when there are sufficiant changes that may impact route calculation (at the moment, I've only come accross a couple of crossings that have been converted to roundabouts; so no biggie).
My dealer did tell me that Kenwood intends to change the presentation of the navigation data, in order to have it resemble the newer portable Garmin units. According to him this would be done by means of a map update (which seems quite impossible to me). Mind you, he is also the one who said that the 8220 has a gyro, and that the CD has to remain in the 5220 for updates, so take it with a big grain of salt.
Jörg