Born Wolf went through four versions (each version has 10 mini versions, v1.2, v1.3, v1.4 etc) and three editors before it was ready for publication. I judged that we as a team spent no less than 18 hours on the final final (v4.6) version before it went to print. It hurts, it's a long process, and in my experience it doesn't get any easier. If it was easy, I'm fairly certain something would be wrong.
I wouldn't limit yourself to submit by the end of the month, because if you leave time between read throughs, you are more likely to spot little errors (it took us until v4.5 to realise I'd given one of the characters the wrong name in a scene. famously the 4th Harry Potter book was published to the masses with the same error, only the character in question had also been dead for 4 chapters) in the text. otherwise your brain just reads what it thinks should be there.
Good luck, and happy editing