I sent 40 nerds earlier today to attack buildings. One for each building. I think it was around 8 hours to complete each building attack. Throughout the day I was getting rewarded for their attacks. But not for nearly as much as the total suggested and much quicker than 8 hours.
Then I sent 10 to one building and it said 1 hr to complete. That hour passed and I got the entire reward. Hope that helps.
And you can see how much you are supposed to earn from every house you attack. I didn't pay attention to each house, but it know the castle is a higher payout. And the more defended/upgraded the castle is, the longer it takes. I'm not sure if the reward is higher though.
