Joshua -
FWIW I think Matt is right. He is just saying (or reminding) that the 17 years is the 95% level – it isn’t some kind of sacrosanct definitive proof – it’s just a statistical expectation.
You could get statistical significance from 15 years or 13 – but you wouldn’t expect it more than 19 out of 20 times like you would with 17 years.