If the case is actively being underwritten I would say probably up to 6 months after that I would expect underwriters to start getting nervous. If you are shopping it I would expect the new company wanting fresher labs. Maybe our resident underwriter will answer.
"Most" companies will take them within the last 6 months. If the client is young(mid-30s and younger), no health history, and the labs are normal I've stretched it to 12 months.