$5M a year seems like it would be very reasonable. The original 90-day price tag was $820M, and they've spent an additional ~$200M over the past decade and a

$5M a year seems like it would be very reasonable. The original 90-day price tag was $820M, and they've spent an additional ~$200M over the past decade and a half. Maybe it's really not worth it to spend $5M/year to extend the life further, but the scientific returns would have to be quite severely diminishing.