Opinion 1: Leave your computer on 24 hours a day, seven days a week to avoid the heat-up/cool-down cycles that may shorten the life of chips and other electronic components.
Opinion 2: Televisions have electronic components, too, and nobody leaves a TV on 24/7/365 to make it last longer.
Opinion 3: Every time you shut down a computer, you cut its life-span by one hour.
Is it better to turn your computer off each day, or to leave it on? Ask a half dozen people, and expect six different opinions.
If there is a clear-cut answer, I can't find it. Nobody seems to have done large-scale studies that compare two groups of computers. One runs constantly for years. The other is turned on and off daily. Which lasts longer?
One reason why nobody has tackled the question in a scientific way: The answer often is irrelevant. Computers have a unique status among other office or household gear. Their physical life-span is much longer than their practical life-span.
Today's typical new computer will be running just fine two or three years from now, whether you leave it on constantly or turn it on and off daily. Computers have few mechanical parts that are liable to break with frequent use. If chips or other electronic components are going to fail, they'll probably die when the computer is brand new.
Nevertheless, computer technology is advancing so fast that within a year or two, you'll WISH the darn thing would break so you can justify buying a new computer with modern features.
Some computers must be left on 24 hours a day.
Among them are computers used as “servers” on networks. Such computers provide services such as file sharing, access to a shared printer, or Internet access to other computers on the network. Turn them off, and other networked computers would no longer have access to those services.
Computers on networks in which the administrator needs access to each terminal (for upgrading software or backing up files) at night or on weekends also must be left on.
For others, let the user decide.
I know just one persuasive technical argument for rebooting - turning a computer on and off - rather than leaving it on 24/7/365. It's based on a little-recognized benefit of periodic reboots.
Rebooting once a week clears errors that can accumulate in random access memory (RAM) chips, and reduce performance. Here's an example of what can happen. Open a program, and it reserves a chunk of RAM for its personal use. Close the program, and the RAM is supposed to be released for use by other programs.
Sometimes, however, the “reserved” sign mistakenly remains on that block of RAM. Over a period of days or weeks, megabytes of RAM may become unusable because programs have left their “reserved” signs in place. Your computer may slow down, or warn that it is low on memory or “system resources.”
A periodic reboot clears out the RAM chips, and makes the full amount of memory in your computer available once again.
We use the “turn-it-off rule” for the three desktop computers at home for a practical reason: To cut electric bills. I figure that leaving one PC on would waste about 50 cents worth of electricity each day. That's $184 annually per computer, or about $552 for three. It also saves summer air-conditioning costs to remove the heat those PCs generate.
The oldest PC has been turned on and off several times a day for four years, and still works perfectly. We've saved enough in electricity to add plenty of extra features to its replacement - if the darned thing ever dies!
Michael Woods is the Blade's science editor. Email him at firstname.lastname@example.org.