I believe that documentation is only needed when it is or will be used. In our team are some people that are just started programming and some people are experienced. The experienced people (who are the youngest!) are developing and documenting a code library very well. The beginners are learning fast with the good documentation. We choose to document IN the code and generate the documentation with a doc-generator tool to keep the documentation up-to-date and this works very stratifying. My experience is that the more people that are involved in the project the more time is spend on documentation to keep everybody focused on the target.

Greetings Dennis.