As far as I know (with one exception) changes have been incremental additions to functionality.
Between discobot and reviewing your site specific user guides every now and then you can keep things up to date, but I suspect that once you’re built a certain level of community your users will start helping each other. We’ve reached a point where the users generally explain things to each other, or point people with questions to the user guides. I used to check the guides for veracity after every update, but now I just wait for someone to point out that the UX has changed significantly from the guide and update it accordingly.