Although I'm still growing my GTD habits, I use the ClearContext IMS, which does enforce some level of discipline on my e-mail organization, which becomes a reflection of my open loops.
I think of the overall structure of my life as a hierarchical collection of "programs," which are like projects, except that they never end.
Within each program/sub-program is an "active projects" folder. That's where projects go.
When I review, if a project is done, BUT leads to another, I update the folder name.
If it's simply done, I move it to an archive folder.
If it's dead in the water, I either delete it or move it to Someday/Maybe.
This enables me to avoid having to track things like each week's status update as a separate project. "Status updates sent timely and complete" is a little program, and every week, it surfaces in my review, and spawns the appropriate next action.
Hope this helps.