Surprised no one else has answered your question. I'm still kinda new to this, but I can now speak more authoritatively than I could even yesterday. Because today I got my second "no, thanks" from Will. This was for a puzzle I submitted in mid-November...which is to say, two and a half months ago. My first "no, thanks" was for a puzzle I'd submitted one month later. So if Will had a problem with multiple submissions at once, I'm sure he would have told me.
By the way, I have 4 more puzzles I sent since then, including one just a few days ago. So I, for one, was operating under the belief that multiple submissions were fine.
Even the first one took a month for him to respond, which I am led to believe is on the quick side. So I wouldn't yet worry after just one week.
Good luck to you!