I use org-mode as a TO-DO list: I setup a list of things to do, assign time estimates to them, schedule them, and clock-in/clock-out. One of my goals is to see how much time is actually spent on my to-dos versus the amount of time I allocate to them. 

One problem is what to do with completed tasks. They clutter up my todo list so I usually archive them to another file. My problem is that after archiving them, I can't compare the 'effort' with the actual 'clock time' easily (i.e. using `C-c C-x C-c     (org-agenda-columns)` doesn't return the same results in my original org file as it does in the archived file.)

**What's a workflow that will allow me to open up my archived TO-DOs to evaluate them?**