The first office action was received about four months ago, and we submitted a response to the action just a couple of days ago. What is the maximum time until we hear back from the patent office (USPTO, in this case)? I am aware that applicants are provided a maximum of 6 months to provide a response to an office action. Does the same duration apply to the office as well?
They do not have a hard limit by statute (like you do) but you can (possibly) get time added to the end of your patent term if they exceed 4 months.
Under 35 U.S.C. 154 b 1 A they need to - (ii) respond to a reply under section 132, or to an appeal taken under section 134, within 4 months after the date on which the reply was filed or the appeal was taken . . .
However the patent term extension calculation is complicated, and depends on timely actions by you. The USPTO interpretations of the formula for it have been challenged a couple of times and the USPTO lost.