Oooo goody... an algebra problem (and they said I'd never use algebra in the real world).
After crunching the numbers (which was so easy a caveman could have done it), the answer is no. 'x' would not = 15%, rather 'x' would = 18.3% (+/- .002%). That means those extra 26 years cost the average consumer an extra 3%. I guess bigger isn't always better.