I am almost finished with a huge novel I've been working on for a while, and I've been learning new things about my characters all the way until the end. If you're still learning new things, I think that's amazing, and it's not something that should cause you worry. In fact, it means your characters still have a story to tell.

I don't think you need to know everything about your characters or your plot. Things will change during NaNo crunch time, and new ideas will probably replace old ones.

If you already know everything about your plot, where's the adventure come November?

I can only hope that my story still has some surprises to throw at me.

Best of luck to you!