I don't dry hop any set number of days after I start fermentation.
I dry hop a # of days in reference to what I want to DRINK the beer at it's peak.
I make a beer, ferment it out, condition it, and then when I want it on tap in about two weeks, I dry hop the heck out of it from no less than 7 days, and as many as 20 days, with leaf hops. I try to do this warm. I usually then get the beer off the hops, and serve on tap. The beer peaks around a month or so after I add the dry hops (anywhere from 1-4 oz). I don't think it would be any different if I bottled. I know sometimes you want to rush a beer, but I'd rather have AWESOME hoppy beers than to have a pretty-good hoppy beer quickly. And in my process, this is what I find gives me the best hoppy beers (IPAs and small DIPAs)