When crates are not updated in a long time, their style starts to drift from the latest style (or the latest style drifts for them) and consequently they do not gain the latest rustdoc features. I think it would be nice if crates which were last updated one or two years ago are rerun and the docs updated with the latest rustdoc.

This could be low priority so that it does not slow down documentation of new crates.

If a compilation fails for whatever reason, of course the old version should be retained.