The more I have up there, the more I sell. There seems to be some cross contamination, in the sense that if they like one of my shots, perhaps they get recommended others. It's not a good return for the hours put in though. The digital enhancements, getting any dust spots out of the sky, etc, takes time, keywording is time consuming. Here's an article I wrote about it, before they cut the rate to 40%. It's lower for new joiners until you get a certain number of photos up there. https://medium.com/feedium/ive-made-over-3000-selling-licences-to-use-my-photographs-e5797cc6ca8