[whpalmer4]

Install Rob Trew's excellent Where in OF script. Invoke the following search:

tasks where (completed is false) and (creation date ≤ today - 16d) and (flagged is false) and (it is not root task of its containing project) --sh cl=a st=incomplete

which will select all of the matching actions. Right-click and select Set Flag.

There, you've just flagged all incomplete actions created at least 16 days ago. The script will remember your search for future use, so you only have to type it in once, and you can install the script in the OF toolbar. Add a daily repeating action to remind yourself to run the script, if needed.

I suppose it wouldn't be too terribly difficult to cobble together a script that did this (so you could run it automatically from iCal), but automating such simple things isn't high on my priority list...