/www.apache.org/dist should contain the latest release in each branch that is currently under development. When development ceases on a version branch, releases of that branch should be removed from /dist.
For example, if Apache Foo 1.2.x is a newer release in the same line as Foo 1.1.a, then 1.1.a should be moved to the archive when 1.2.x is released.
If Apache Foo 1.2 is a new branch, and development continues on 1.1 in parallel, then it is acceptable to serve both 1.5.a and 1.6.x from /dist.