Please explain to me how I am 'wildly off'. If you buy a 2005 model car that has been sitting on the lot for 5 years is it magically a 2010 model???? I did NOT say it had been ridden for 6 years (I know it is easier to just jump to conclusions rather than read the actual text), but this bike is no way, no how a 2006 model as the OP claimed.
Lets assume that I am completely wrong, and the frame is (gasp) a 2005(really a 2004 that was shipped late), and he bought it in 2006, and the OP has a reciept, and he bought it new. It is still WAY out of warranty, a model that was last mfg in 2004, and a design that has seen three newer itterations. (lets also assume that the OP did not bring up ANY of these extenuating circumstances in his post because that make soooo much sense).
Just 'cuz' lets pretend that RFXs did not sell and were not in demand, and somehow the frame was bought new last month. It STILL is a 6 year old design that has undergone three significant changes. Find any 6 year old object in you house..stove, couch, TV, computer, skateboard, washer, shelving unit, place setting, window, whatever you imagine...... and try to find an original replacement part for it regardless of price.
What is also possible is that the OP bought a 2006 and then purchased a used (who know how old, or how abused) HL rear end put that on his frame assuming it would 'ride better' (pretty plausable based on the questioning of TNT/horst differences that were beat to death years ago). STILL the parts in question are second hand, out of warranty, and 6 years old....
Please find me another company that would have parts (the OP alluded to the ability to 'get' a TNT rear) for a 6 year old design, and would actually cover rear stay parts at this age.
It is an old bike that is ridden in the mountains. Sh1t breaks when it gets old.
The standard here is NOT what every whiny bike rider wants it to be (and lets be honest an unbiased at least this time and agree that a large portion of MTB warranty expectations would be absolutely laughable (see this thread, ie rock damage) in any other industry)....it IS what the industry supports. No matter how you look at it, support of any kind for a frame this old (not to mention the $500 trade in, forum support, refurbish program) is far beyond the industry norm.
"manufacturer defect" seems to be a term that bicycle consumer have a very hard time understanding.