I've written 3,500 words in the new and as-yet-untitled book (I have it saved as "four" since it's the fourth in the series), but it's not the first 3,500 words. I've been jumping from high point to high point, writing a bit here and a bit there. I suppose I can link the scenes up later, but I suspect I'll have a lot of rewriting to do.
I didn't used to skip ahead. I still don't, except with the weredeer novels. I wrote a small scene for book three when I had just started work on book two, and after that it's as if I'd given myself permission to jump around. I think it's because I know these characters and this world so well, and I know what's going to happen in future books; I want to hurry and get to the good stuff. It's sort of like making quilt squares; but eventually I have to sew all the squares together and hope I got all the sizes and colors right.
I don't quilt, actually. But hopefully my analogy wasn't too off, for those of you who do quilt.