Fingerprinting!!

We have an FBI biometric fingerprinting date!

I've heard about people walking in after they've received notice of their appointment and getting the prints done sooner.  Does anyone have experience with this?  I will have to take time off to do the fingerprinting, so I really don't want to go as a walk-in and have it be a waste of time.  Our date is October 11th, so it's not that long to wait, but certainly if we can do it sooner I want to!  We'll go in Nasvhille, and I would love to hear from other people who have already done the biometric printing and have done a walk-in appointment.  This is a big step for us, and one big step closer to Katie!