The point is...
When your team meets or you discuss some functionality with a fellow developer, you use the diagrams?
In case affirmative, then the use must be everyday, therefore is rewarding the work of keeping the documentation up to date.
In case negative, probably the diagrams were made only for an initial understanding or to fulfill a customer or management expectation, so it’s not worth it, because work is more than the benefit earned.
Considerations
If the diagram source file is versioned together with the source code, then it is easy for any team member to update the diagram and Sincronize the project with SCM.
On the other hand, if the team usually works with printed documents, simply scratch the document in pencil and it will be enough to use in the next sprints (provided, of course, that no one plays basketball with the papers and a waste basket).
UML diagrams need not be a 100% accurate reflection of the code. In many cases, I avoid putting attributes in classes to avoid compromising the internal structure.
But what often happens is to use UML to represent the system’s database model. I don’t agree with that very much. There are more suitable tools that allow to make an MER (Entity-Relationship Model) and already synchronize the diagram with the database.
Despite the title of the cited article (I don’t have the full article), none of the sources (Fowler, Ambler) suggests that UML is not documentation. On the contrary: Again the UML is Useful here, providing the Diagrams are Selective to help Communication.
– utluiz
No doubt it helps communicate, but it does not imply that it is documentation. This is described in the linked article.
– Juliano Alves
What I am saying is that the sources that the linked article cites do not prove the past idea, nor does the author provide an appropriate definition of documentation. In fact, the standard definition of documentation according to the main authors of Software Engineering involves precisely the communicating, then either the author wanted to be somewhat controversial, or he used an alternative definition of documentation.
– utluiz