A tower controller from DTW used to hang out at our FBO occasionally and BS. He told me that they have huge pushes and then they usually twiddle their thumbs for a couple hours until the next push. He told me anytime I wanted to come down and do touch and gos in my 150 just give him a call and he could give me the right time to do it. He said they regulary had guys do patterns in the middle of the day as long as they weren't busy. Never actually did it, but it would have been fun.