Just curious, how would your mortgage payment compare if you refinanced to a 15-year? The length wouldn't be that much longer (15 years versus 13 years), and I think 15-years are now running in the low 2% range.
Also, how much does having that mortgage payment bother you? I struggle with the whole "pay off the mortgage" debate on a regular basis. In my case, I have about $2.5M in invested assets. 29 years left on a 30-year mortgage at 2.875%. The original balance was $468K, but I think I'm down to about $455K now. The principal/interest portion of the payment is about $1941/mo.
Sometimes I'll think, I could pay the mortgage in full, and still be over the $2M mark. And sometimes I do like the idea of eliminating that $1941/mo payment (although it's less when you factor in the tax writeoff).
I've also thought about doing little "mind tricks" to pay the mortgage down faster. Such as, for example, every time my invested assets hit a new goal, I pay down $50K or $100K or whatever. But, unless I refinance, that doesn't change the monthly payment; all it does is moves the payoff date up. And then I start thinking along the lines of, who cares if it's paid off when I'm 70, versus 80 for example. And, over time, thanks to inflation, that $1941/mo becomes less and less significant. So, I guess analysis paralysis sets in, and I end up doing absolutely nothing