I have an '07 Overland with VES. I have updated the dvd for navigation that includes not only newer maps but firmware for the unit. I have never heard of any updates for the VES system nor can I imagine what could be updated for a somewhat simple movie dvd player.
I just bought a used 07 Overland. Leaving the dealership, we tried plugging in our address to get home. It wasn't in there because our house was too new. So we told them and they installed an updated disc about a week later. I didn't notice anything too significant with between the old disc and the new one except for the added streets. Even the case was the same.
Mine still has the 06 disk, the latest is a late 09 cd from the dealer, navteq or ebay. You can find a torrent online but they are difficult to burn. 1x speed, specific burning software, udf mode. gps underground forum reports it is the same Map as the 2006 af cd that I have. I tried the early 09 version, AG, and it was the same map. Getting the newest AI version now but don't have yet. We'll see.
The maps are truley updated with every new version. I know this because I have seen changes in the maps in my region, and I have gone through a few versions of the nav dvd.
I don't know how they go about updating the maps - if they choose certain regions to add with each new one or just whatever new comes in. Keep in mind they also update the POIs, and I can also say there are more than previous.
If your dvd gets you around the region where you drive without any issues, there's no need to get a newer one!