That's an interesting problem. The right answer mostly depends on the distribution of crashes at time t since deactivating autopilot. I would personally guess the relevance of autopilot fades to near 0 once you're 30 seconds since deactivation for 99.9% of crashes.

5 feels a little too aggressive, but would probably capture the majority of the true positives. I would have picked 10-15 seconds based on my gut.