The novel I just sent to beta readers was started in November 2007, written to about 60K words, and then abandoned. Why abandoned? Mostly because it was *supposed* to have been a short novel (a Nano project) and it wasn't done by the end of November. Or December. I had a software (AKA "paying") project that I had put aside to do Nano, and I had to pick it up again. That took longer than expected too.
In November 2010, I decided the book should be un-abandoned. Because the idea was just too cool.

So I did a read-and-edit through the 10 chapters already written. I went through the outline for the remaining chapters. I found my notes made when I was working on the story and read those. And then I just picked up where I left off. The story finished right at 100K words, then grew another few hundred words when I edited it before sending it out.
I don't think the "seam" between where I stopped and picked it up 3 years later is visible. But I guess I'll find out when the beta readers get back to me. =)
-David