I agree with the dismay over leaving a blanket on for two weeks.

Holy cow, man, that's just straight crazy talk. I knew some people who had 6 horses. They would blanket once- the first weather that "needed" a blanket they went on, and they stayed on. Pure laziness if you ask me.

IF I blanket, it comes off as soon as possible.

Rain in and of itself does not cause rain scald. If horses have a good nutrition program, a place to get out of the rain if they desire and a clean paddock, rain scald can be unheard of, regardless of how much it rains. (although I have not experienced the PNW, and may be wrong)