This really needs to be implemented soon. The key differentiator of Asana is its flexibility to quickly set up things and get going. In a nutshell, Asana allows to do rapid prototyping of managment flows which is extremely powerful because at the beginning of a project it is not yet clear what is the best way to manage it. It is therefore decremental to the product value if this flexibility comes with the cost of:
a) either lose part of the information or
b) accumulate old, outdated information
The lack of this feature attackes the core value proposition of the product. I am a big advocate of Asana but this needs to be prioritized and added soon.