It kinda is what it is with computer. The longer they run without rebooting the more often they run into issues. I used to know the exact reason this occurred, but it's been awhile. I believe the longer a computer is running without reboot, the more likely it is that information loaded into RAM gets corrupted. So an occasional reboot is definitely a good thing.
Indeed, the longer a system is up and running the more fragmented the operating files and data become, eventually a failure or crash will happen without a reboot.