Another thing to consider is the tax benefit you get by contributing to your 401k. Depending on your tax rate it could easily mean thousands of dollars if you're maxing it. You'd have to calculate it with your #s but it could be higher than what you could save by using that same $ to pay off your mortgage

OP just as a hypothetical: you could buy a 30Y Treasury yielding 3.746% today and you'd make almost as much interest than what you'd be charged on your mortgage (3.9%).

In other words, you have a pretty good rate considering current rates. From a strictly numbers standpoint there is no need to pay it off quickly