I have been running Archiva as it existed in snapshot 20 November 2006.
When running in Tomcat with the standard memory setting it fails after a few days.
Increasing -Xmx=128m increases the time but it still gets and OutOfMemory error after a few days.
This is with no activity. I came back today after the weekend and hit refresh on a Pom page and it gave the OOM. It seems to be time dependent. At home I have been running it on Mac OS X. I saw an OutOfMemory error after a week. I did even go to a page to check it. The running console had it.
To reproduce simply run up archiva and leave it running.
We are working around with a nightly restart.