A few things: First, the technology choices are secondary to the organization that is charged with maintaining it. If the organization goes out of business and

A few things: First, the technology choices are secondary to the organization that is charged with maintaining it. If the organization goes out of business and the software doesn't get picked up then it's lost. The exception to this would be widely used open source software. Second, use boring technology that's easily extensible. If it's easier to build a new thing to replace the old rather than extending it, then it probably won't last. Finally, the purpose of the software must stand the test of time. Think about the patterns/things in life that will still be here decades from now. For example, death and taxes :)