Original estimated lifetime
"Certainly, keeping the lights on a bit longer and putting off the expensive moment when a replacement must be launched is a double benefit."
I understand the description as "win win" and the benefits of extending the life of the satelite, thus delaying the cost of launching a replacement, but if it's 17 years into a 13 year mission, surely they costed that out 20 years ago and expected to launch a replacement at least 4 years ago? Or was not really financially viable at the time of original launch? Or is just that sweating the assets means more pennies for the upper echelons of the company? What if it had failed sometime in the last 4 years, ie past it's sell-by date?