Cleanup and Maintenance Scripts - are the already installed?

Are most OSX cleanup and maintenence scripts already installed in the OS? I have never made or isntalled any scripts myself. So does OSX already do what it needs to do overnight while I am gone, or should I get some automated maintenance and cleanup going?

I do not shut down or sleep my computer. It's a mac pro, runs all night. Been up for 8 days so far this time.