Why aren't you using the Delta Data Migration (DDM) tool that BMC provides? That is the typical process for keeping your new staging environment up to date with data from your current production system.
Alternatively, you could use something like RRR\Chive
We use our Customer Move Tool (more info http://www.alderstone.com/cmt) to migrate from previous ITSM versions to the latest, we can migrate all ITSM data (foundation, config, transaction) as well as delta data. We have out of the box mappings from 7.6.04 to the new 9.1.02 allowing you to easily move data without the need to write any scripts or configure mappings.
Also because we are data model aware we can move all related information (CI's, SLA's, associations etc) as well as all background data. We've been able to move entire data set within a day ensuring a smooth migration and upgrades. Reducing cutover window and minimising change freeze on the production environment to make the upgrade a "non event" for the business.
Please let me know if you would like to talk about this in more detail or have any specific questions.
Yes the delta data migration is usually used to move the delta data created
during upgrade phase.
You have the option to specify start date and end date which will perform
migration of data.