I built
http://bookexchange.usu.edu/ and it still runs on OpenACS 3.2.5 (with some mods) and has ran for the past 2.5 years.
At the beginning and ending of semesters the 20,000 USU students pound on that site like there's no tomorrow, trying to sell their books or buy books for less from other students. We get around 8,000 unique visitors per day on those periods of the year.
Almost all of the pages hit the database, and for the 2.5 years the site has run, it has run almost unnatended and without almost no maintenance. We keep daily backups, but thanfully never needed them. The machine was a simple K6-2 300 machine with 256 MiB of RAM.
-Roberto
