Many fields, in the world of consumer electronics, are getting more and more similar to the world of computing: we are getting fast replacements of former models, and the new ones are often small variations with a number of improvements which might, or not, justify the jump.
The manufacturers are always selling their new models as a significant replacement, one which deserves the expense. And every year, users are confronted to new models tempting their credit cards.
Computers have been suffering this situation for a long time. But in the world photography, prior to the arrival of digital cameras, you could be fairly sure to use SLR model for many years without significant drawbacks.
And something tells me that, looking quietly, it might still be the case, despite the manufacturer's propaganda.
Let's use my personal example for description.
In 2005 I got a Fujifilm Finepix F30, after reading extensive information on its capabilities in the net. At the time, its main quality was a peerless reply to low light, and a ver high image quality in most situations, for a compact camera. It is a 6 megapixels model, and it is limited to jpeg, no raw shooting.
In 2006 I got a Pentax K10D, for many reasons, the main being the very good image quality, the large number of features, and the huge compatibility with all kind of Pentax lenses. The problems were a somehow spotty autofocus, and a less than stellar response to low light.
Since those dates, both kind of cameras, compacts and digital SLR, have made tremendous advances, so that today you have compacts which blow away the F30 and K10D. Furthermore, a new category of cameras, the mirrorless models with interchangeable lenses, has appeared in recent years, mixing the best of both worlds.
But if we go to the key question: are those new advances significant, so that I should replace those cameras? Moreover, are the prices of the new cameras going to be compensated by their better features?
I honestly am unsure, and rather I would say "no".
I am an amateur photographer, who works in different matters for a living. I shoot as often as I can, usually on weekends when we do trips to other cities, or doing sight-seeing in the countryside. Under those conditions, both the F30 and K10D keep on doing a fine job for my needs.
6 megapixels are more than enough for most of my casual pictures, taken on the fly while walking around. And the F30 really shines in low light, even if there are current models that far outcompete it. It is a pleasure to use, the focus is nailed most of the times, and it is a simple, no brainer camera to make a quick, great shoot without any further consideration. It still leaves you some manual controls, and I have done some truly stunning shoots at night using them with attention.
Something similar happens with my beloved K10D: 10 megapixels seem ridiculous in front of today's crazy contest for more megapixels in every generation. But to me it is largely sufficient, and if you add the countless possibilities of this camera, I have plenty of opportunities to play and have fun. I swear I have not yet discovered all its capabilities, despite having utilized extensively since its purchase. But for an advanced amateur, I think it easily exceeds your expectations. I could obviously do with a better autofocus, and also with an improved sensor for very dark shots. Yet I managed to make some absolutely terrific shots with it and, most importantly, it has been great fun to use and learn how to use the Pentax K10D. The picture of the Mezquita on top of the Guadalquivir river, in Córdoba, which illustrates this post, is one of my best shots and it was done on a rainy night with the K10D. Furthermore, thanks in significant part to the articles posted by Mike Johnston at The Online Photographer, and to the back catalogue of inexpensive prime lensees from Pentax, I started playing with primes and I think I have been hooked for life.
In short: the camera manufacturers will keep on trying to hook up users to switch to their very last impressive model. But yours truly is planning to contradict them and keep my cameras for a long time, before switching.