My shortest job hunt took about a month, but I was a cheap junior dev then. These days, I'm constantly getting pinged by recruiters, but I know better than to take that as evidence that finding a new job would be easy.
My last job hunt took almost 6 months (ok, I was being a bit selective). Hell, finding someone that didn't balk when I told them my current salary (and I was looking for a job in a fairly low COL area) took at least a month (and I'm too old to care about foosball tables and free lattes).
And now my current job has been eroding pay/benefits and layering on useless processes and other BS. I can feel that itch coming on... better budget a year to be safe.