The documentation doesn't explain what is the maintenanceWindow is, as during patching a node switch happens, why this window length matter at all? Could it impact the duration that the Redis cache is not available to use?
What is the maintenance window? When scheduling updates for Azure Redis Cache, you can decide the day of the week, start UTC hour and maintenance window. Setting a maintenance window allows you to minimize the impact on your application and users. Only Redis server updates are made during the scheduled maintenance window. The maintenance window does not apply to Azure updates or updates to the VM operating system.
What is the impact of setting a shorter or longer window? The default and minimum, maintenance window for updates is five hours. The actual time required for maintenance depends on exactly what’s taking place. You could always set it to a longer timespan, but we recommend selecting a timespan that would have the least impact on your business.