Lately it seemed to be down more than up. It seemed that every time I wanted to use it for something, I would have to drag myself downstairs and perform a hard reboot because the login process had quit working.
After I had to restart it again on Saturday, I called up the reboot script and set it to daily.
Then I thought, "If I am having to reboot this thing daily, I should really look into seeing why it is becoming so unstable."
I knew that it had some issues because its system log was a sea of red and yellow errors and warnings every time I checked.
I plugged a couple of the more frequent error codes into Google, and it led me to a discussion board where somebody had been experiencing similar problems. The responses were unhelpful, but he edited his post to say that he had managed to fix it on his own, and he outlined the steps he'd taken. He ran a couple of internal diagnostic and repair jobs in Windows, and then manually re-enabled one of the network services that had somehow been disabled.
I followed the same steps that he outlined, restarted the machine, and it has been stable ever since. I still had it set to reboot daily, but I cut the frequency to Sun/Wed/Fri again this evening to see how it goes. If it doesn't seem to be having any issues, then I will cut it to just Sunday restarts, and ultimately go back to the monthly schedule that I originally had it on before I upped it to weekly.