Make it so media cache destinations are remembered in the project file.
When I open more than one project, the media cache destination stays the same. Each project file should have an assigned media cache folder that doesn't change. I notice also when I switch hard drives (I have to for this company, no dedicated media server) and switch back, the project file doesn't automatically recognize the original media cache and creates a default on my internal HD. I have to do it manually every time, hopefully without it creating too many cache files that I have to find and delete later.
Steve Hagelman commented
I have a dedicated media cache drive and whenever I open Premiere without the drive plugged in it goes to the internal drive--which is fine if it would revert back to my dedicated media cache drive the next time I boot it up. As a result I have a lot of files on my computer I don't want on my computer. It'd be nice if it remembered the external is my preferred drive, across projects, even when it isn't plugged in and maybe move any internal drive files there or at least ask me at start-up "Hey, I'm going to be putting cache files on your internal drive, you okay with that?"
Jim Simon commented
Media Cache is set for the system, not at the project level.
For this reason, a dedicated Cache drive is recommended.