A bad hires are expensive mistake if you can't get rid of them until some artificial annual event. While I understand onboarding complexities, my experience is that the teams/companies which hasn't create good automated process so new hire can commit their first change within 2-days are big red flag (this was insisted upon by Zuck extensively at Facebook scale). I would also argue that culture of hire/replace team members in agile manner would help enforce this process more naturally and vice versa.