So a few things here. First, it shouldn't take more than a few minutes to build and write the cache file. It first builds it in memory and then tries to write it to the intended directory. The users folder is pretty light on permissions, which is why we chose to write the databases there. I'm looking into your specific case now. I think I need to add more logging to figure out precisely what the issue is.
We're wrapping up this weeks build, and then I will get logging into the end of week build for you if possible.