It is folly to plan an ERP project in too much detail, but this is not true of a cutover plan.  At cutover, there are so many interdependent processes, shutting off access to old systems, extract-transform-load (and all the validations that come with it, turning on new integrations, shutting of old ones …

Cutover requires a highly detailed plan, including an hour-by-hour schedule, as well as communications, signoffs, and fallback options.