Microsoft offers Office 2013 Home & Student (discounted) on third-party key sites like StackSocial or CDKeys for as low as $20-$30. These are legitimate, single-use keys. Add the official ISO from Microsoft, and you have a safe, preactivated (via legal key) system without the crack.
While Microsoft rarely sues individual home users, using unlicensed software in a business environment can result in audits, fines, and legal fees. The Business Software Alliance (BSA) actively tracks corporate use of preactivated software. Microsoft Office 2013 64 Bit Preactivated Download
A: Most KMS activations last 180 days. The preactivated installer should include a "renewal task" in Windows Task Scheduler that runs every 7 days. If that task was deleted by your antivirus, activation will expire. Microsoft offers Office 2013 Home & Student (discounted)