90 Days
Update: July 27, 2021 — I’ve changed my mind. I now think the correct number is 30 days.
A tip to hiring at startups: If someone is not essential in the first three months, let them go.
Startup work is never-ending, and it requires a proactive approach to work versus reactive work.
Given that a new hire is brought on board only once the pain is felt, they should already have plenty to do in their first 90 days, even without being proactive in taking on and learning new things.