As typically for mac maintenance questions, I've heard various opinions on this. Somewhere I read that if your computer was always turned off or in sleep during the time when the maintenance scripts were supposed to run that they wouldn't run and that your system performance would degrade. There is a command you can enter in Terminal to find out when they last ran. I don't have it with me, something like -al var/log/*.out
When I do that I usually see that they ran fairly recently. You know that there are three; the daily, weekly, and monthly. They clean up your caches and some other stuff, and you might be able to find a description if you search the web. I found the command for finding out when they last ran and the description of what the scripts did somewhere on the web.
Even so, I sometimes run them from Terminal; it can't hurt. Not 100% certain on the syntax without my reference, but I believe the command is:
sudo periodic daily weekly monthly
It will ask for your administrators password, and you will know it is complete when you get the prompt following your root directory with '%' (otherwise there isn't anything to tell you it is running.
Oh, and you don't have to run all three.
P.S. Be careful with what you do with sudo, as the warning will tell you, but it is hard to screw up the with periodic maintenance scripts.
