For those who are making screencasts of their software, some observations:
1) making multiple short screencasts that are very focused on a particular idea is 100x easier than trying to make one big long screencast; plus it has to be easier on the user. i think 2-4 minutes is the sweet spot.
2) you'd be surprised how long it takes to explain something -- so plan to focus really narrowly.
3) doing a bunch of screencasts one after the other can be quite productive -- once your mind gets into the flow of speaking while you are using the software, it gets more comfortable. so plan to sit there and do quite a few retakes before you start to get comfortable, and then do a bunch of them in a row.
4) if you're aiming for doing lots of screencasts quickly, instead of perfecting each one, then just keep restarting the recording until you get it right, rather than try to edit it post production.