I've got the same trouble with my 99 taurus. I was wondering if it was a light level sensor that was causing the problem. I defogged the lights with special cleaner, but that wasn't it. At least the lights are clearer.
I guess at the end of the day you're asking, why is this guy driving a 99 taurus?
Well, the thing is in great shape and I want to keep it going. This model year was obviously better made than most. I can't remember a day when ford made a car that would still like great after 12 years of normal use. But I digress.....