As photographers we all have moments when the latest shiny new lens or camera is released and we read the reviews, check the specifications and look at the price. How much??? is my usual first reaction.
It is surprising how quickly we can adjust mentally from 'Nice to have' to 'Should have' to 'Must have'. We justify in our minds the usage benefits, the quality of images and the need to stay current.
As a business what we should be looking at is whether this shiny new addition to our camera bag will actually earn us money and will it increase our earnings over and above that produced by our current kit. The answer is usually no but that does not stop us popping the latest must have item into the on-line basket. Sitting on the screen when it could be sitting in the bag it is only a mouse click away. The 'Buy' button taunts us. Are you man enough to click me it seems to be saying.
We can offset part of the purchase by selling an older lens or camera. That is not too bad then. Actually it is probably good. It is not really a squillion pounds it is half that when we sell this other stuff. A bargain really.
The older camera or lens can be our new back up. The fact the current back up has not come out of the bag for 18 months is not really that important is it?
Don't do it. There you go. Decision made. Wait for the 'must have merchants' to upgrade their perfectly good kit and then wait a bit more. Eighteen months after a new body is released is a good time to look for its predecessor in the second hand market. Any issues will be known about and someone else will have taken the major part of the depreciation hit.
Lenses depreciate slower than bodies and wear out or age far slower as well. Unless it is a real bargain I tend to buy lenses new rather than second hand. New camera bodies are released every 12 to 18 months to replace the current model. Is your current camera on its last legs? If the answer is no and it is doing the job well enough then give it a little pet and thank it for saving you a lot of money and earning your living.