Websites offering "lifetime generators" often contain viruses or ransomware that can lock your files. It is safer to use the free web versions of Word and Excel at Office.com if you don't have a valid key.
Instead of using a generator, you can find your actual key or activate the software through legitimate methods: Legitimate Ways to Get/Find a Key microsoft-office-2013-product-key-generator-for-lifetime
The most "interesting" aspect of searching for a is that these tools are almost exclusively malware or scams , as authentic software keys cannot be generated by third-party programs. microsoft-office-2013-product-key-generator-for-lifetime