I realize most people dream of being mortgage free, but in my mind it makes more sense to extend your 2.75% mortgage for as long as you can., keep those credit cards and lines of credit paid off, and invest your disposable income. Most mutual funds are performing around 5 to 8 percent right now, which puts you earning at least 2.25% over the cost of borrowing for your mortgage. Once you accumulate a substantial portfolio and achieve a comfort level, expand into self directed investments such as buying stocks.
Even back in the early 90's when I purchased my first home at 16% I believe it was, I followed this philosophy as mutual funds were returning over 20%. Even when I purchased another home, I put down the minimum from the equity in my old home, signed up for another 25 year mortgage to keep my mortgage cost down and my disposable income up and invested the rest of the equity. It was just a matter of time before my dividend checks were in effect paying my mortgage.
With compound interest, the earlier you start investing, the richer you will be.