Such settings are stored as Site Preferences in permissions.sqlite, so make sure that you do not clear the Site Preferences. Changes made in "Tools > Page Info > Permissions" apply instantly and do not require confirmation just like Option/Preference changes made via about:preferences.

Clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows and software installation (permissions.sqlite) and password exceptions (logins.json) and other website specific data (content-prefs.sqlite).

I don't believe these settings are saved in Windows 7 (even as admin).

Every single page that I've tested this on always reverts the setting changes I make to the default settings. After just a few tries it's obvious these setting changes are not stored.

I don't want to be a dick, but your reply wasn't the answer I was hoping for, in that it was an answer based on some documentation somewhere, but it's easy enough to try and see for yourself that changes are not only not stored, but the changes are not even changes, since nothing changes once you close the Page Info box.

I don't know why I bothered to post this question, but good job making an attempt, I guess.

I have attached a screenshot that shows the permissions.sqlite file with the SQLite Manager extension that shows the microphone and camera setting that I temporarily made for the YouTube website for this purpose. These settings are still there after restarting Firefox and also show in "Tools > Page Info > Permissions".

Changes made in the Page Info dialog should be saved immediately when changed. After you close the Page Info dialog, if you click the padlock/globe icon in the address bar, are the modified permissions displayed on the drop-down panel at that point? How quickly are they lost, for example, when closing the last tab open to the site, closing the window, closing Firefox, etc.

(I haven't personally given those permissions to any site.)