Charles Chandler said:

So it's ashes to ashes, and dusty plasmas all of the way back to dusty plasmas in the end.

The evidence seems to favor a Sun that is not losing mass, due to the extremely sparse nature of the interplanetary medium. So it looks more like the Sun actually just cools down with age, and will eventually freeze over. Still, the power per mass loss calculation is useful, even if the matter is getting recycled, because when the matter is being expelled, power is being released, so there is a direct relationship there. Over time, the same amount of expulsion will generate less power, but the energy budget stays the same. It's just that with the same original energy store, the net mass of the Sun stays the same, while the watts per kilogram of expulsion go down.