I don't know of any productivity tool that handles archiving well. You can store done tasks in some way, but all the context is lost. Over time, it's annoying even on a small - individual - scale.
yeah, the info is there and you can do the same with most tools, but it often requires a lot to extract it. how well organized is it? how hard is it to go from line of code to complete discussion around when it was last changed?