This. Follow the exact steps.

I just did in Dec last year. Once the application submitted and fees paid, I scheduled for an interview.
Turn up to the embassy an hour before the time following the exact instruction given. No electronic, big bags and so on.
Went in for the interview, follow the queue as instructed, and answered exactly 3 questions;

1. Which state are you visiting?
2. What is the purpose of the visit?
3. Who is funding this visit?

Total of 45 seconds interview. The officer informed "approved" and passport will be ready for collection/delivery immediately once answered all the questions.
Interview time at 8am and out of embassy at 820am.

10 years. I applied the visa for a conference visit in Atlanta. So maybe professional given 10 years automatically.