One database that I'm working with has been in continuous use since SQL Server 7 in 1999. The major app on top of it has been totally rewritten 5 times, each time with different UI technologies. We're now entering discussions regarding rewrite iteration #6, leaning towards using MVC and jQuery for the UI.

The major app has also acquired several "bolt-on" satellite apps over the years that use a subset of the main database and major app's functionality, along with their own SQL Server databases.

It just keeps on going and growing...