The non response sucks. You're not alone. I've had publishers interested and then that's it. Nothing more, when you were interested and everything and then I'm just dropped just like that? Yep. That's how it goes on some of these publishers. It's a business, it's nothing against you personally, I hope you get that. But for me, there has got to be an ending time, regardless if I hear back or not. I give it 6 months and if nothing, then I assume that aren't interested. Now granted, I've had full requests 18 months after the submission was sent. BUT that only happened to me that one time that was the longest from submission to full request. You never really know until you get the email. There are more and more of them that just don't respond if they're not interested. Unfortunately, yes, it's the standard thing and becoming more and more popular, even with small presses.

I would go over all the submission guidelines again and see if you missed something. Sometimes they will say it, sometimes they don't. If you wanted to, you can nudge after the 6 month mark, but most likely you won't hear back. BUT I have heard back the couple of times I've done it in the past, so it's worth doing your homework on and double checking all your pending submissions.