If you are asking how to convert an evaluation version of Windows Server 2022 to a production version, please refer to https://docs.microsoft.com/en-us/windows-server/get-started/upgrade-conversion-options. If you are asking about the expiration of the current VNext Insider builds, we will publish newer builds with a later expiration date before the current date expires, and a simple build-to-build upgrade will then extend the expiration date for you.
22538 is not an Evaluation version of Windows Server 2022. 22538 is a preview version of Windows Server VNext (the branding in the preview has not been updated yet). Evaluation version of Windows Server 2022 may be obtained here: https://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-2022. The Evaluation edition may be converted to production with the appropriate product key. Hope this helps.
The certificate will be updated long before the current one expires. Rather than staying on a preview build for weeks or months, we encourage you to upgrade to newer builds as they are released in order to pick up new functionality and bug fixes.