About the CDT and upgrades and maintenance
Using the Configuration Deployment Tool should not impact the methodology for applying upgrades or fix packs in a multi-step staging environment.
The upgrade methodology being followed should not change for environments already set up for staging before production. However, the Configuration Deployment Tool by itself does not provide support for all of the processes and methodologies required for supporting a multi-step application staging and deployment environment because it is only capable of deploying configuration data.
The process of applying product upgrades and fix packs is especially complex in an environment where the staging area must be kept synchronized with production. One way to keep these environments harmonious is to apply software fix packs to both systems simultaneously and reverse deploy the data upgrades. This is because application data upgrades may behave differently and produce different results based on the transactional data they encounter. If this application data upgrade is run independently on production and staging, the results may be significantly different as a result of the differences in transactional data that the upgrade program encountered. In such a case, the production snapshot should be treated as the baseline and reverse deployed into staging. This can be accomplished by configuring your production database as the source and your staging database as the target.