I'm due to interview someone tomorrow who has had 20 jobs in 25 years... a few 6-month contract positions but mostly 12-18 months in 'permanent' roles. I'd estimate that most of the roles would have been on project-based work of >2yrs duration.

I'm keeping an open mind - this person isn't ruled out but it's difficult not to read something into the possibility that they've never seen through a project.