Time to withdraw submission?

I submitted a short story in mid-July to a speculative fiction magazine. Although the submission guidelines do not provide an estimate for the response time, the averages on Duotrope indicate most stories seem to be accepted or rejected within 6 weeks; I checked recently, and Duotrope has now received reports of responses to submissions made in September.

I have yet to receive any response, or even an acknowledgment of the submission (and yes, I have checked my spam folder). Last week, on the three-month anniversary of the submission, I emailed a query to the editor, but have not received a response to that either.

For all I know, my emails are going into the editor's spam folder, and he hasn't received any of them and never will. I'm not assuming any ill will or particular failure by the editor, but if he's not going to get to it for whatever reason, I'd like to send my story elsewhere.

So what do you think? Time to withdraw the submission, or should I give it another month?

Thanks, all. Per Duotrope, the maximum reported response time seems to be 75 days; I'm 3 weeks beyond that. No simultaneous submissions allowed, but I'll give it a month and query again at the end.