Google Earth uses images from various sources, and they are of varied resolutions and ages. The higher population or more interesting areas tend to be in higher resolutions, and therefore clearer, because they usually get scanned more often. This is general, but not the rule. Mostly it has to do with availability of the images. Some areas are almost entirely available in Hi-Res.
The photos on average tend to be 2-3 years old, some quite newer, and some quite older. I have seen the photos of my home update 3 times in the last couple of years. Keep checking back, one day it may be updated.
You can view the date of the photo by selecting the DC-Coverage boxes.
When they update the software, it is just the interface. The photos downloaded from a server while you zoom in on them. All versions of GE use the same photos pay plan or free.