It's two weeks later, but yesterday I read an article about strength in the One Power and aging. These charts are extrapolations based on explicit power level/life expectancy correlations from RJ. This is without any Oaths, and as these are averages, "a very few" channelers would actually live...
"Spit dog" is referring to a small dog that would run inside of a basket like a hamster wheel to turn the roasting spit over the fire. "Brindle" is a coloration meaning the dog has dark streaks or flecks.