until a product is "finished" there is much that you can do, such as the basics of online help, overview documentation, etc. Part of the challenge of adopting an agile approach is adopting an agile attitude. The usual question one asks is to emphasize what is impossible. An agile attitude is to ask what is possible.
If your product lifecycle permits, you can dedicate one iteration to completing the artifacts necessary for shipping the application and performing release stabilization if needed. A stabilization iteration is a short iteration focused on final integration testing, documentation, and the like. While not strictly part of an agile process (since you should be doing all of these things as you go), a stabilization iteration is a useful tool when you are transitioning to agile or when you have a demand for extensive supporting activities
that need to be done after the bulk of the feature work is done. You would do your stabilization work based off of a Release Prep Codeline.
Another common concern is how to address a need for complicated manual integration testing. An agile approach is also pragmatic. An agile approach also highlights potential problems with your architecture and development process. Teams also have a need for complicated (and sometimes) manual integration testing because their architecture is
complicated and they have not developed their code in a way that enables automated testing. Strive to have as much automated integration testing as possible during your iteration. Then use a stabilization iteration approach to do any remaining required testing.
The ITIL framework in its new V3 release now covers release management as part of the Service Transition book. One of the factors for many organizations is that the process of releasing requires handing over to operations, and integration with existing live systems and services. In such circumstances, documentation and ongoing maintainability are very important.
A related issue is that in many organizations your are not starting to develop a totally new application. You are instead enhancing an existing application and delivering some extra functionality. How many project teams spend the first part of their development trying to understand the existing system and its interfaces and dependencies, before being able to reliably change it. And then the project team disbands, a new one comes along and the whole wasteful process is repeated.
So in these situations the appropriate level of documentation is vital. One advantage of development methods which use lots of automation around testing (unit tests, automated system and acceptance tests) is that as long as the tests are maintained, they provide a very real source of documentation and also a safety net for future changes - being able to prove you have added functionality without breaking existing functionality.
Agility is about delivering value predictably. Taking an agile approach to your Release Planning process will help you meet the goals in your release plan and allow you to be more confident in your commitments.