While I agree with previous posters that your example of increase sale is not an open ended project but instead a higher level item I find that I have many open ended projects that really are projects.
The more standard GTD system calls anything you maintain as an area of focus. However there are also supposed to be relatively few areas of focus. I find those things to be mutually exclusive in my world. If an AOF is only stuff you maintain then I have several hundred of them. However standard GTD seems to call roles as AOF and not really things you maintain.
Instances within an AOF of specific items can be managed as GTD projects. I make AOFs much larger: Stuff like manage sheep flock are subsets of the manage the farm sustainably AOF and within that are on-going projects of the regular vaccinations, wormings, hoof trims, shearing and so on that are part and parcel of farming. I guess the difference is that while I consider projects that come back around to be open ended other people don't.
So I think GTD principals can easily be used to manage open ended or recurring projects. Each specific instance is a reasonable project with a defined end, even if it's arbitrary. I do a lot of things based on the calendar so project may repeat several times in the year or once a year but they are still projects.
So while I think your example is not an open ended project I thing GTD can mange open ended projects.
Oogie McGuire - Mac, iPhone & Omnifocus
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Paonia, CO USA