I agree with Jon about virtually all routine maintenance being in the status of "if it aint broke, don't fix it.". Over the years, the increased stability and functionality of OS X has rendered most routine maintenance unnecessary if not altogether obsolete. However, I do run regular checks of the volume and file structures as well as surface scans to provide early warning of impending system problems, but I do not consider these tests as maintenance as no files or data is changed by them.
