The production outage depends on the migration method and the time needed to save, transfer, restore and test the final workload. The overall project also includes preparation, software checks and a rehearsal.
Measure those jobs with a representative recovery set before scheduling the switch. Replication can reduce the final data transfer, but the plan still needs synchronization and business acceptance. A server model alone does not establish a dependable duration.
Use a migration rehearsal to measure the final save, restore and business acceptance work before scheduling the outage.