I did it three times, in 2007, 2010, and 2012. Each of these were 8-10 months. The key is that you can't spend your time on the couch. You need to have a story. Live in a foreign country. Write a book, even if it doesn't get published. Spend some time working on an open source library that you've always wanted to help out. Walk the Appalachian Trail. Ideally, you're spending 5-10 hours each week (after an initial decompression) keeping up with the industry and keeping your programming skills fresh.
When you start, make sure to write down all of your stories and accomplishments so that you can come back and interview like you never left.
And have twice as much money in reserve as you think you need, because your job search after the fact will take a little longer. However, you will find a job again.
This, as long as it led to something genuinely interesting/useful and/or relevant to the work, and you can demonstrate it somehow, no one serious is going to perceive it negatively after some questions and answers.
When you start, make sure to write down all of your stories and accomplishments so that you can come back and interview like you never left.
And have twice as much money in reserve as you think you need, because your job search after the fact will take a little longer. However, you will find a job again.