applescrap
Be the ball!
I generally go about 3 days. It's not because 24 hours isn't enough- it probably is- but just because it seems a bit short.
I've found that I get the best brightest hops flavor and aroma with a total of about 3 days, more or less. I've gone longer when circumstances mean I have to wait, sometimes much longer, but 3 days is my sweet spot.
I will also dryhop in the keg, at 40 degrees, through the life of the keg sometimes. I haven't picked up any grassy notes, but it does take quite a bit longer at cold temperatures to extract the hops oils.
This.