Unless your in a rush, dry hop after or close to FG (12 - 30 days depending on how big the beer is). I typically will dry hop 5-7 days once I am close enough to finishing FG that I know it'll be done by time dry hop period has finished. Did Yoopers house pale ale I was in rush to have done for a party, had in primary 14 days (was pretty close to FG) so dry hopped in keg while carbonating and was ready to drink 3 weeks after brewing it...tasted great too!