This is a tricky one. My new WIP is off to my editor. I thought it was ready. (My agent didn't)
I've seen people send things off way too early. I've also seen the opposite. I've seen people over-revise. They keep getting feedback and keep reworking and reworking until the story has lost some of its original appeal.
So, how do you know when you have hit that "sweet' spot. The place where it is time to submit.
I think a good writer has to trust her instincts on this. Did I feel like there was no way my manuscript could be improved? No. It's not about being "perfect". It's about being "irresistible." I felt like any editor who read it would love it enough to want to work with me on "perfecting" it.
Not to sound conceited, but I felt that it was too charming and compelling to pass up. That's the time to send it out. When you can't imagine anyone would say 'no."
When you can drop it in the mailbox and walk away with a huge smile on your face.