You've not uploaded anything for nearly two years. Motion conversions aside, you've not created anything new in nearly four years. With ever increasing competition from more items, and newer items... I don't think there's anywhere for your sales to go but down.
Are you not planning to make new items? It's apparent you know what you're doing when it comes to AE and Motion, and a few decent new items could make you an extra couple of grand a month, based on the sales figures from your Photo Gallery item.