I am pretty frustrated with the sensor dirt issue on the A7. I don't change lenses that often (I only have 2, and they are zooms), don't use the camera in dirty/dusty environments and take care to keep the body angled down during changes. I use the A7 in prety much the same fashion as I used the DSLRs I had before it, and yet never once had a need to clean sensor in many years with the DSLRs. Is it possible that zooms are a factor? (Pumping air as the lens is zoomed) What else am I maybe doing to cause the problem?