Last night one of my CP's asked me when I was going to send out my MS for querying. I replied, I want to look through it again to make sure I haven't missed something--there is something off with the ending, but I don't know what (Note: I figured out what just before bed last night, now have to fix it). She laughed and reminded me that I could keep going over it and tweaking it forever.
And she's right. I could. I try to read through and make only the necessary changes, and find myself line editing instead of reading for flow and only stopping when I get pulled out of the story.
So, how do you know when it's time to put down the editing (and the track changes) and polish up that query letter and send it out into the world?