I get less of them on istock than SS or FT, perhaps they don't make it as obvious when one is required? Price can't be anything to do with it because some sell for more on FT.
Correct. I got a couple of extended ones this month on SS and On Demands almost daily (Feb 09). At the contrary, my trend on DT was increasing subscription. I don't know if this trend is true for everybody but this makes SS suddenly by far my most profitable site, despite the subscription. You might be right, SS communicating and enforcing its license policy much better.