We use Wrike for our in-house marketing team and we do probably 100-200+ projects/tasks a month. We keep everything we do in one space, and when things are done we just close out the project and that's it. We reference back to a lot of old projects throughout the year so we don't really archive things as we go. What I do, though, is once we near the end of the year I create a new "Archive YEAR" space, and I move everything to that space and start the new year fresh within the same space that everyone is already working in.
This allows us to start in a clean space and not have to weed through years worth of work, but also allows us to reference back to stuff from years past (which we do regularly). But it also doesn't freak people out when things change. They just continue working in the same area that they were, but on the back end I'm just keeping everything clean for everyone and they know to reference to the archive spaces if they need anything.