My process is that 60 days before the end of my current contract, whether my current client has said they intend to renew or not, I start seeking other contract opportunities. If my client finalizes the renewal, I halt my job search. If they don’t, the 60 day window has consistently been long enough to ensure I have my next client lined up before my current contract ends.
Most of my contracts are 12 months long. I don’t take contracts any shorter than 6 months.
I should note that I’m in Canada and so I don’t have to worry about healthcare coverage.