GAS (gear acquisition syndrome) is like an addictive drug. Over time the satisfaction with a "normal" dose lowers and you'll need more GAS to get the same level of pleasure.
So, as we head into the camera buying season—particularly since we have quite a few amazing cameras to consider—you need to ask yourself a simple question: "if I buy this new X how long will I be happy with it?"
If you can't see yourself satisfied with any of the most recent cameras for at least four or five years of photography—and probably many more than that—you probably are a GAS addict and are in need of an intervention.
That last paragraph, by the way, is the answer to those not interested in moving from a DSLR to a mirrorless system (additional commentary was posted today over at dslrbodies.com). If you were to buy a Nikon D850 today, for example, I'd bet that you'd get four, five, six, or maybe even eight years of great photography from it. Amortized over five years, a new D850 today works out to the equivalent of a US$40 month subscription. So there's another metric you can apply: are you using your camera enough to justify paying US$40 this month for it? If not, why are you looking at cameras, at all?
Historically, if you were using about two-and-a-half rolls of film a month at the start of the DSLR era (1999), you'd have been paying about the equivalent of US$40 month (after accounting for inflation). That's today's equivalent of one Starbucks Pumpkin Spice Latte about every four days (less in states that tax it). What makes me think that some of you are going to use this in your defense of a camera purchase to your spouse? ;~)
Ultimately, you shouldn't be getting out the credit card and ordering up a new camera unless one of two things are going to happen: (1) it will make you happy; or (2) it will make you money. So for almost all of you reading this, we're back to the headline: how long will that happiness last?
The marketing departments at the camera companies would probably answer "no more than two years." The CEOs at the credit card companies would probably answer "not at all, you need to buy another." Fan boys will agree with those CEOs: "not at all, you bought the wrong one." Your significant other probably has the answer closest to right: "why did you need to buy a new camera at all?"
Yes, Thom is playing Grinch this year (or almost any year ;~). But he also knows that come the end of February, when we've seen the next onslaught of amazing new cameras, you'll be looking at them fondly and thinking maybe you need another shot of GAS.
