Freedom Since 1999
The answer to your question is "it depends", but when doing the analysis, remember to adjust for risk. Paying down the mortgage provides a guaranteed rate of return, i.e., it's a risk-free investment. There are some investments (e.g., stocks) with higher expected returns, but these carry a lot more risk than paying down the mortgage.
We paid ours off with an inheritance in '99, and have NEVER regretted it. It allowed us to save the monthly mortgage pmt., invest it, and (combined with other aggressive savings and conservative investment approaches), ER in 2012 (about 3 yrs. sooner than expected). In our situation, the peace of mind was priceless, as my husband has a disabling lung condition which we feared could require an early retirement.
He actually worked longer than expected; but we could not put a price on enjoying this house for as long we like, downsizing when it fits
our schedule.
Plus, I remember reading the spreadsheets that showed how much interest we would be paying the bank over the life of the mortgage. It was in the hundreds of thousands. So, when we eliminated that bank debt from our future, we chose to put those dollars into our own pockets instead.
We did, and it worked. So, it has felt like a 14-year coup de grace. I feel like a "little guy" on Main Street, USA, who "beat the system." Rather than lining the banks' coffers, we lined our own.
Granted, this is not a rocket science investment approach. But it has served us well.
Best of luck with your decision!