How long does it take to write a book?

I’ve been wondering how long it really takes for an author to write a book. I’m not talking about a first draft, I’m talking about the point where an author says “done!” and then sends it off to the publisher or agent. For me, it usually takes about six months to write a draft worthy of revision. But to consider the manuscript completed it takes a lot longer. Since all of my books have been through the ringer with agents, editors, and publishers and I’ve used their advice and my continuing literary improvement to keep revising and strengthening both plot and grammar, the maturation process for each book has taken a long time. Here are the time frames it took to consider each of my novels complete and off-to-the-publisher-worthy. I have many more books to come.

TIM MADISON GALACTIC WARRIOR 1996-2003…7 years
http://www.amazon.com/Madison-Galacti...

INSECTLAND 1997-2011… 14 years
http://www.amazon.com/dp/B005P81J48

FROSTPROOF 1998-2009… 11 years
http://www.amazon.com/FROSTPROOF-N-D-...

PULP 1999-2010… 11 years
http://www.amazon.com/PULP-novella-N-...

DEGENERATES 2000-2009… 9 years
http://www.amazon.com/Degenerates-N-D...

AFTER. 2001-2011… 10 years
http://www.amazon.com/dp/B0050Q8D8U

DROP OUT 2007-2011… 4 years
http://www.amazon.com/dp/B005FX0K7U