IMO, as long as you have a good yeast starter and good fermentable wort, 8 days will work. Instead of dry hopping, a few times I have chilled the wort down to 180-170 and added some aroma hops. I let them sit for about 20 minutes at that temp and then continue to chill the wort.
I did this a few times back in CA when I brewed with Beverage Bob that see on the forums. Not quite the same as dry hopping, but a viable substitute IMO. I would say most of my ales are done fermenting in 3-5 days anyway.