@Nageswar Cloning of instance is the common and best practice way of maintaining data between a PROD and DEV environment, and should be part of a scheduled or agreed process to ensure a Dev environment is operating with the latest updates and features.
If a Dev environment is not receiving clones, it's entirely possible for the environment to fall out of sync across a year and this can be lead to development issues.
Another method of potentially syncing data is just exporting the Userlist via XML and then importing it.
You can also add Users to an update set using the Add to Update Set, and then move that update set manually to PROD.
