I am terrible when it comes to selling camera gear I own. To be in on the product cycles, it is imperative that one has to sell the older gear to buy the new. No exceptions at all (unless you are reviewer and have access to the latest free of cost). Without new gear, photography sucks.
What is the average best life time of a new camera to sell to have the least impact on the finances? Let us overlook the currency value fluctuations that would put this whole game in a different territory altogether.
Any advice would be greatly appreciated.