As you say David, we have a real mixture of owners on here, and I guess I fall into the last two of your categories...
I think I also fall into the category, as many others do, of "rapidly changing Audi S/RS owner profile syndrome". What I mean by this is that our intentions and aspirations tend to change over the period of ownership, and often quite quickly.
In my case, when I acquired my S4 just over 2 years ago, I thought that my ownership would last for possibly 2 years before I either got "bored" or felt it was time to move on. As I had found a highly (factory) spec'd stock car, I had no real intentions of doing much in the way of modifying, other than perhaps a remap.
Well, those of you who know me (and my car) will know that this changed after about 9 months of ownership when I bumped into MRC back in the days when they were touring the country with their box of tricks...(now where's Dazzer - he's to blame for this!

). Since the initial remap last June, it's been 18" wheels (2 sets), 710Ns, Samco hoses, RS4 exhaust and gutted downpipes, AWE DTS, RS4 bumper, short-shifter, AWE ICs, APR bi-pipe, snub mount, RS4 B7 front brakes, a few cosmetics, and AWE boost gauge to go on soon...
During this last year, I've been backwards and forwards between going the K04 route or moving up to a proper RS4 (B5 of course) - I always thought that would be my next step.
However, you will have no noticed my more recent flirtation with the RS6...

So now I've got that bug, my head's just in a complete spin...I want it NOW, but I don't have the funds right now and anyway I feel I should get at least another year's use of the S4 to justify all the money I've spent on her...and now I'm stressing about not being able to fit in a fully modded S4 or an RS4 before the RS6...decisions, decisions!
Now, as a general rule, I don't like (or drive) automatics or estate cars, but IMHO the Audi avants and tiptronics from the RS stable are in a completely different league...

so an RS6 is now on my radar...
The only question is when and how (saloon or avant). In an ideal world, I'd keep the S4 saloon and go for an RS6 avant...and I think we all know what would happen to the S4...
Rather a long answer to a simple question, but I'm chilling out after last night's Christmas party...

but the short answer is "keep it as long as possible, with the ultimate goal of an RS6, and possibly an RS4 on the way"...
So what are your intentions David?