Jim:
I think the reason for this constant churn is the possition of mirrorless cameras in the market place. Sony is attempting to displace an existing product (DSLRs) with a still developing product (A7 series). The A7 cameras have not yet matured to the point where each generation is only incrementally different from the last. Whole new features (IBIS, EFCS, etc.) are appearing with each new model so owners feel left behind and are willing to trade up to get these new features. I guess it's the curse of a new platform.
If this phenomenom only recently occurred with the introduction of the a7 line I would tend to agree with you but sadly it has been a roller coaster ride since the a900 and the introduction of the first SLT's. The wave of enthuesiasm then disgust to another models enthuesiasm to yet another degree of disgust a month or two later. Same goes for the lenses as well....... Bottomline is for some the excitement to photography is
in the chase of technological advancements (that seem to never quench this thirst) where others it is in the capture of light
with whatever they have in their hands.
Both are all well and good and I am not telling anyone what they should enjoy about this activity it is just new readers need to recognize these differences in those posting and not click "buy" when they hear something is
the best thing since buttered bread. Only to see the techno hoards that promoted XYZ running away from the product (they just bought a month or two ago) selling them at a loss in their hurry and buying the newer and greatest for this month model ABC or make MNO.
It is not just a a7 phenomenom unfortunately .........