Unity is not designed with an expectation that it should be rebooted weekly, it's designed to be able to be kept up and running with no reboots needed. That said, if you are running a pre-2.4.5 version, I would suggest rebooting regularly because we did have some problems with memory leaks. If you are running the most current version, 2.4(6.135) you should be okay without rebooting weekly.
Jami Stewart
Cisco Systems