Permanent exterior signage is crafted to be durable, and can certainly withstand your normal rainy/frosty/foggy PNW weather season.
At least in theory.
While it's not the highest task on your to-do list -especially during a rain-soaked busy week-you will benefit from performing a preventative monthly signage check to keep problems at bay down the road. Permanent signage solutions have a long shelf life as long as they're maintained with some regularity and updated when it's required.
So what are you looking for when you give your exterior signage the once-over? Common sense takes care of most of this. Look out for rust, mold, standing water, paint discoloration and broken hardware. Obviously, if your sign (or the base or frame it's held up with) isn't made of wood, these are not deal breakers. Mold should be cleaned off immediately to prevent preading (plus it's unsightly and doesn't leave the best impression of your business). Paint discoloration could be a result of a number of factors that affect the longevity of your investment. Does your sign have brackets or a frame that has visible space you can stick a finger-width into? Open it and make sure there aren't any critters nesting inside and there isn't a buildup of dirt, mold, excess water or unidentified objects