An app and database I designed and built back in 1999 (go live date) is still going today. It was SQL 7, Now it is running on sql 2012.

I was an employee of the company way back then. The app has had a small amount of development over the years , perhaps 30-40 hours a year. It has survived 3 take overs (I only survived 2!!) and I still do development on it as a contractor (self employed for last 7 years) . The only changes are generally enhancements or where Accounting standards have changed so we need to alter a calculation. Easy stuff unfortunately, can never really charge enough to live on that one. But based on its reliable performance I get lots of other great development jobs.