2 weeks to get a "we have received your letter and will read it" letter (twice this year) and about 1-1.5 months to get a response (once this year, second one hasn't gotten the response yet but is only 3 weeks old).

But both were pretty weird policy/system issues that didn't warrant a "standard" response or resolution (and for which I specifically said I was not looking for compensation), so that may make them slow to process. (The reply to the first issue, in fact, implied the writer completely missed the point.)