We are trading away disk space for faster builds. We could make them faster in some cases by using even more...

On the other hand, it would be good to garbage collect those caches. We are wrapping up work on a new layout for intermediate build artifacts that will make it easier to GC them.

Sounds like what I was thinking, that or for third party deps to go into the same temp folder, and anything not accessed in over a week, or so just gets auto wiped by rustc / cargo build process?

Can you talk a little more about that? How would that work, and what would the developer experience be like when using it?