It appears the oldest images are from about 1999 and the most recent ones come as they are served... 2005 being the most recent reported.
The airfield locations of course remain the same.
I have a requirement to compile a list of UK "flying sites" past and present, but in decimal lat long format for plotting and xml output. Every now and then I generate an index and publish some pages for general interest.
When I`ve completed it I'll make it available as a freebie download so anyone that's interested can use it as they wish.. eg Google Earth, WorldWind or whatever.