Question for the financial wizards here.
Background:
I have decent net worth, building up to retire at the latest at age 40 in 2020. I have a car loan at 2.9% interest, and a mortgage at 3.375%. (BTW, I'd sell the new car, but it was for the wife anyway, and I haven't yet convinced her of the mustachian benefits. We'll own it for a minimum of 10 years and 200k miles. Plus the luxury is, well, luxurious). No other debt.
Is it better to pay off loans sooner or invest money, expecting double the interest rate that I'm paying?