Notable is that it's not the actual half-life of the Pu238 that causes the majority of the performance regression, but the degradation of the materials that convert the temperature differential into electricity.
In other words, they could have lasted a lot longer. But of course they've outlasted their design life many times over.
Would be interesting to see if any of the probes survive 50 years in space. More impressive if V1 continues to transmit beyond 1 light day. That would be June 2028.
So the transmission distance with respect to the rotation of the planet the probe was launched from at the time it was launched. I suppose that is more sophisticated than a unit which is somehow derived from the width of a horse's ass.
I'm thinking if the metric system was invented today, distance would be based on a light second somehow.