Universal Containers is about to begin the release of a major project.

Refreshing all non-preview sandboxes during the release preview window is the best way to handle the situation of having a mix of preview and non-preview instances for the release of a major project. A release preview window is a period of time before a Salesforce seasonal release, where the customers can test their applications and integrations in a sandbox that has the same version as the upcoming release. By refreshing all non-preview sandboxes during this window, the architect can ensure that all the sandboxes are aligned with the same version and avoid any conflicts or errors during the deployment. Refreshing the sandboxes when the release management team has time, mixing instance types, or contacting support to rollback the release are not good practices, as they can cause inconsistency, confusion, or disruption in the release process.