If s/he hasn't heard back, don't waste your time worrying about what some mythical, widely-held expectation is re. hearing back.  These are big bureaucracies.  Expectation differs from function.  There is no golden rule.  FOIA the file. 

A very cool little birdie recently told me about this other thing you can to do follow up on a FOIA.  It's called an administrative tracking request, and it looks something like this: 

<<I, [so-and-so US citizen, in this duly notarized letter] hereby request a copy of the administrative tracking/processing file/folder (including but not limited to documents, correspondence, memos, notes, and emails) for the following FOIA requests (or appeals): xyz.  You may omit the underlying records requested in those requests (or appeals).>>

In this case, your relative probably wants to FOIA the file, get it, contest inaccuracies in writing, complain to the top (following chain of command does not work in your favor here), wait out the appeal (if applicable), and THEN request the administrative processing record.