What preventive maintenance do servers need on a regular basis?

We recommend quarterly preventive maintenance: update firmware/BIOS to stable versions (improving compatibility and security), clean chassis dust (poor cooling accelerates aging), check and tighten loose data and power cables, replace power-supply capacitors older than 3 years of runtime, and verify backup restorability. ZhongLianDa maintenance contracts include preventive maintenance: we agree on a maintenance window in advance, take full backups before operating, and deliver a report afterwards.