They seem to have started keeping some programmes available for longer, which is great. But the logic of it all escapes me. I've been catching up on ISIHAC: at the weekend they had episodes 5 and 6 available only for another 2 days, but 10 days for episode 3. However, episode 6 is still there and apparently available for another 6 days, as is 3. So why would the older episode be available for longer? And what happened to no. 4?