Hmmm. I should go back and read what Mr. Money mustache says about killing your mortgage. I've been listening to a lot of Dave Ramsey lately, and he talked a lot about the peace of mind when you have no debt and no payments to make anywhere, ever. For me it's a tossup. I love investing, I would like to buy real estate investments, I enjoy the stock market. And, I understand that's when I pay the money into the mortgage it's a locked up.
Perhaps the answer is a compromise, I would love to kill the mortgage earlier. We are also on a 15 year with a low interest rate. And hacking one third of the time off of the mortgage would be awesome. I would love to have it out-of-the-way at an earlier age. Then again, if I can invest and I know I can invest fairly well, I should be able to outpace the mortgage rate.
I read several articles about the various risks. There is a risk that you miss out on investments, there is a risk that your investment returns are not as good as you think they're going to be, there is the risk that you sink money into the mortgage get laid off, and then can't pay it off. (although, this doesn't really apply to us, because we could wrangle things to pay it off now, it's just not very convenient.)
Paying my mortgage every month has never been a severe worry. So I guess for me investing still makes the most sense. I like the flexibility of having cash that is liquid and easy to access and if for some reason paying off the mortgage becomes an urgent issue, we should be able to do that.
For future real estate investments, I want to be very careful with the debt levels, and hopefully be in a position where those are also easy to pay off should the need arise.