I have an iMac running on version 10.9.2. The processor is an Intel Core I4 (2.7 GHz) and 4 GB of RAM. At times the operating system is very slow to the point where I can't do anything. I can hear the computer spinning quite a bit when this happens. The problem is much less after I reboot. Does this IMac need to restarted regularly. If so how I often? I typically rarely restart it. I have an older macbook air with less RAM and a slower processor that never has issues with speed and freezing up. Any other suggestions to optimize performance of the IMac would be greatly appreciated as well.