I think you need time between drafts but maybe just a few days UNTIL you are absolutely sick of writing the manuscript or until you're certain you've revised as much as you can. Then I think you need to let the manuscript set for a much longer period--a month. You aren't seeing it anymore. You're in love with certain sentences or paragraphs or even chapters and you've gotten attached to them. You've become close to your characters. Too close. They're real now. They're like real people. You've been with them for months and months. How can you cut them or even radically change them? They're yours. It would be betrayal. What kind of a person are you?You admit-- a word here and there in the manuscript can be changed. Fine. Tighten the language. Sure. At this point even if your critique group says there's something wrong, you're going to secretly think the something that is wrong is THEM.
You have manuscript blindness.
The good news is it's not a permanent condition.
It's a point we all reach. I read something by Stephen King where he was saying that when he gives his manuscripts a big rest between drafting and revision, like five weeks, he always find something big he's missed. Something big. Even Stephen King, writer of a million novels, is susceptible to manuscript blindness.
At some point, when you've lived in the world of your novel for a long time, you just can't see what might not be working. You need the distance of time. You need fresh eyes. On that first time back to your manuscript it's important that you be brutally honest with yourself. You won't see the manuscript that freshly again until it's been accepted and you're working with an editor. Go into revision being open to major changes and you will improve your manuscript.
Or so I think today.