As per Chris Null's article, he spoke with the "good folks at Seagate" about harddrive wear & tear and ...
apparently starting and stopping is not a huge problem with harddrives any more, and they can be safely shut off and on in order to save power. According to Seagate, you can expect a drive to last for three to five years of running time before dying, though obviously many drives last longer. What's the big factor that causes drives to die early? Heat, says Seagate. Ensuring your computer stays cool through the proper use of fans is far and away the best thing you can do to keep your drive healthy. I'd imagine that shutting it down when not in use will only help. Naturally, shutting down your computer will also conserve electricity, so unless there's a compelling reason to leave it on (as with a server), you should probably shut down at night.
- mind you a different point of view might interpret Seagate saying this so that you do shut down your pc more often & incur additional wear & tear on your harddrive causing it to fail earlier and forcing you to purchase a new drive.
The more electricity you use the more pollution you cause, as alot of the electricity that we make use of is created by burning fossil fuels which adds more pollutants to our air and contributes to the increase of greenhouse gases. Be power smart, turn off devices when they're not in use and save money on your electric bill and save the environment at the same time. The environment you save today will be the same one your kids will live with & enjoy in the future.