All the options we've been given in the Flash pref pane were previously available to us on Adobe's website, but they were a nuisance to access and didn't seem to be as reliable as far as "sticking" as are the new ones.
My preferences aren't sticking in the Storage tab of the new one. I looked for a suitable plist to trash but can't find it. Does anyone know what it's called and its location?
EDIT: I may have solved the problem. I looked at ~/Library and saw that Caches had been modified today. Looking inside Caches, I found an Adobe folder that had a Flash Player folder inside. That folder had also been modified today. Consequently, I used OnyX to clean caches, restarted, and my preferences had stuck. I'll post back if the problem reappears.
I still don't know where the preference file for Adobe Flash Player is located.