Offer your thoughts or opinion on the input financial query or topic using your financial background.

Pay off entire mortgage or put into investments
I like this option, rather than exposing all 600k to market risk, I'd think of paying off the mortgage as a way to diversify my portfolio. Expose 400k to market risk, and get a guaranteed 3.75% return on that 200k (in essence). Then you can invest the money you were putting towards your mortgage each month.  The potential disadvantage, is that the extra 200k investment could earn significantly more than 3.75%, and you'd lose out on some money. Historically, the market beats 3.75%, and you'd come out ahead investing everything. There's no guarantee. You also don't have to keep your money invested, you can change your position down the road and pay off the house. I feel best about a paid off house, but I know that my sense of security carries opportunity cost. Up to you to decide how much risk you're willing to accept. Also, if you don't have an emergency fund, I'd set up that first and then go from there with investing/paying off house.