I'm not sure how you have your test cases structured, but that sounds more like a system test or acceptance test than a unit test to me.
In my opinion, unit tests should be concerned with testing that functionality works and exercising various code branches. An example of a unit test would be processing a single record, and you might have a few variations of this record to force your testing to go down certain paths and confirm your results are what is expected. Your unit tests can be used for regression and smoke testing as well - things that you run on a regular basis (nightly, after a build, locally in a development environment before a code review, and so on).
Your system level and acceptance tests aren't run as frequently - running automated system tests nightly would be as frequent as I'd expect. These would be more intensive tests that would focus on system performance, memory consumption, timing, and behavior with other systems. Having it automated, much like your unit tests, are a good thing, but I wouldn't want to bog down your unit test suite or regression test suite with such long-running activities.