Has anyone ever had a scintillating scotoma that lasted long?

Yes. If your scotoma lasts longer than 15 minutes permenant retinal damage can occur. The scotoma is caused by constriction of the blood flow to your retina. If the scotoma is close to or covers the center of your vision it is more serious. Treatment can be as simple as an adult low strength Aspirin to anti migraine drugs. Can be caused by other neurological problems full evaluation is reccomended!
Patience. This is a component of ocular migraine, which has its origination in the occipital lobes of the brain. Most are of short duration, minutes to 1 hr, although the visual diminution in the center can be very disturbing. Ocular (occipital) migraine is benign, causes no permanent changes and clears with no after effects. If very frequent, you could seek the help of a neurologist but this is uncommon.