Sorry, I don't follow. I'm on Nightly (the 58-to-be) and I have Firefox configured to use a master password. It seems to come up once per session -- are you shutting down your browser constantly or something? I'm a little confused as to what specifically you don't like. (The one time it comes up is pretty jarring, I'll agree.)
I don't care about having to enter my password once at home. I care much more about having my navigator at work (which syncs all my personal accounts, including bank & government) being unlocked all day long, and much more when I'm not the only one to have admin access to my machine.
57 hasn't been released long enough for me to tell how it'll go... but when I dismiss the prompt once I don't want it to go modal every time firefox tries to sync or every time I click a link on a page I'm not logged in.
