although i have no personal experience with this, the fear of leaving the dry-hops in for too long is that a grassy or vegetal flavor can be extracted.
luckily 1 oz of cascade isn't a huge dry-hop and depending what else you have going on in the beer there may be plenty to cover up any grassiness. i suspect your beer will be fine.
once and it's ready and you taste it, please report back letting us know what the impact was. i'm curious to see if a long dry-hop does have a flavor impact.