I generally put mine to sleep. You can use a tool such as Onyx periodically to run the nightly, weekly and monthly jobs.
BTW, these cleanup scripts are not the same as what you get with Windows' disk cleanup routine. That just automates tasks that you could be running yourself, such as emptying your trash (erm, Recycle Bin) and deleting temporary installer files (of which the Mac doesn't usually have anyway), clearing your browser cache, and deleting "downloaded program files" which is something specific to Internet Explorer (ActiveX stuff, which for security reasons should never be used anyway).
The equivalent on the Mac would mostly involve emptying the trash, clearing your Safari/Firefox cache, and cleaning out /tmp (which should be done automatically at each reboot). Beyond that, a tool such as Spring Cleaning can remove orphaned files such as no-longer needed plist files.