Wouldn't it make sense to have Firefox Portable set the cache folder to a local path and delete it on exit by default? I wonder if it would improve the performance of Firefox Portable...
https://developer.mozilla.org/en-US/docs/Mozilla/Preferences/Mozilla_net... (Specifically browser.cache.disk.parent_directory
)
Disk cache is generally used between sessions. Firefox maintains a current in-use cache in RAM that is lost on exit. The disk cache is primarily for use for things not in RAM. The only time disk cache would help much in the same session is if you did a ton of browsing of different sites that would be more than the RAM cache holds. Or if you visit a site much later than you did last time. But for browsing a handful of sites (even dozens) and hitting multiple pages on each, all the images, CSS, JS, etc will remain in Firefox's RAM cache.
Sometimes, the impossible can become possible, if you're awesome!