[brianogilvie]

It was discussed a while ago. Early alphas of OmniFocus had a preference to automatically clean up after a user-specified amount of time, but it was never properly implemented and ultimately disappeared.

The problem (for many of us) with immediately cleaning up is that the completed action disappears immediately; if you are afraid you clicked the wrong action, you then have to hit undo and (if it was the right one) redo.

I'd like to see the original preference restored (clean up automatically after a user-specified time delay, which could be immediate). If you would too, use Help > Send Feedback... to get it in the feature request queue.