The case fans are not thermally controlled, they spin at the same rate all the time. The fans on the cpu are speed controlled. These machines are meant to be on 24 hours a day, that's why they have aggressive thermal management. You can power down the machine at night. I only power mine up when I play them and leave them on for a few hours. The issue with keeping it off for too long, is that it will drain the nvram battery and when that happens you have to clear and setup the game again as you change the batteries. Lucky for you the bb2 batteries seem to drain slowly over time. I've had mpu's stored away for a couple of years and the batteries are still good. Now I do the sensible thing, I remove the batteries on my spare mpu's.