Dry hopping
 

What's the shortest amount of time worth to dry hop? I have a few (4 days) before I want to bottle and was thinking of adding a few pellets to take it up a notch.... Will I get a noticeable hop impact for such a short period of time?

A few pellets? Not gonna do anything noticeable regardless of how many days, a few ounces, definitely noticeable in 4 days

yeah, have about 1/2 oz...

It'll make a difference. Is it worth it? That depends on if you're the type of guy who loves buying and throwing hops at every step in making beer or the type that is pinching others hop sacks you're so tight. You'll probably get different aromas in varying quantities that you won't be able to discern much. Good luck.

There are some experiments that say 3-6 hours is more than enough to affect the beer:

http://pubs.acs.org/doi/abs/10.1021/bk-2012-1104.ch013

A typical dryhop for me is an ounce or two for 3-5 days before packaging. It works out great!

I never dry hop for less than 10, and no more than 14. typically 3 oz at the minimum.

I see no reaosn why not to add the pellets for a few days, what does concern me is this statement

"I have a few (4 days) before I want to bottle"

Beer is ready, when its ready...not when you want it to be ready. Obviously a certain level of planning is important because life can get in the way of beer chores, but rushing beer will never do it any favors.

I like the idea how it doesn't matter what form of hop(pellet or whole) you use as aroma extraction occurs easily.
This paper also mentions that different aromas are extracted at different rates, so as time goes on there are differences that will be imparted on the beer. Hydrocarbon terpenes extract quickly peeking at 2 to 3 hours. While terpene alcohols extract slower.
If the OP likes their hydrocarbon terpenes maybe dry hopping the night before or day of may actually be more beneficial. Maybe even pitch what you've got now and pitch more later to get a fuller bouquet.
Alright, who's got 10 gallons of IPA they want to do a hydrocarbon terpene vs. terpene alcohol extraction experiment with?

What the hell, drop em in.

There is another less "scientific" experiment out there where some brewers did several experiments and simply did a taste test. They also came to the conclusion that after 6 hours to a day, there wasn't any major difference. I still do a week though. Can't find the link right now