Ideally I always dry hop for 3 days then keg. Single addition, 3 days, keg.
Question is, Do I run the risk of off flavors (?) if I leave the dry hops in contact for longer then a week?
Yes, you do. Recent research has shown that all the good stuff is extracted in 24-72 hours. After that the hops start reabsorbing the oils which leaves you mainly polyphenols. My experience bears that out.
I routinely dry hop my NEIPAs three days after fermentation starts and leave for 8 days. I do it mostly to reduce/eliminate my chances of oxidation, which i experienced when I tried to DH three days before bottling. My beers turn out good and I haven’t noticed any off flavors because maybe I’m in the cusp. The hops may start to reabsorb oils, but there must be plenty left by the time I bottle.
I usually go between 3 to 5 days before kegging. I think I have gone longer, but don’t remember anything bad happening. But that was probably because I didn’t know any better. LOL.
I also go only three days with dry hops (after fermentation is complete), then keg. Denny swears that dry hopping when the beer is cold is better, but I can’t do that with my setup so I dry hop at around 65 degrees. Could the aroma be better with dry hopping at a lower temperature, probably. But my beers still smell good and taste good, so I subscribe to the mantra “if it ain’t broke, don’t try to fix it” in my brewery. If I ever decide to drop some bucks on a glycol system, then I will dry hop at a lower temperature, but right now that isn’t in my game plan.