The plan almost never turns out perfect when it meets reality. Further, as conditions in the real world change, we need to update and advance the software to match. We will be availbel to work on the post-production processes such as enhancements and fine-tuning of the system.
Additionally, if an issue comes up that needs to be fixed, the developers should be informed in order to provide fixes depending on its severity. The product may need a hot-fix, meaning a fix for high-priority features that should be done as soon as possible, or otherwise, just wait until the next version to apply the updates.