<Does anyone know the average response time >
Well it doesn't appear that specific info is collected by the USPTO and made available to the public. I guess they take as long as they want when responding to anything.
But they do have statistics that indicate the average amount of time from filing of exparte reexam to reexam certificate is 26.5 months.
If I've counted correctly, the 148 patent has been in reexamination mode for 54 months so far. We are long past, past due.
Opty