The math says keep the mortgage.
Assuming you pay off the full 700k for illustration... and the entire sum is subject to 15%
You are going to PAY $805,000 (after tax, assuming you can keep it to 15%), you are basically paying $105,000 to feel good about not having a mortgage.
That same $805,000 will generate $2,600 a month for the rest of your life, or left to grow at a measly 5% return over 30 years, will be something like $3.5MIL
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The math says keep the mortgage, but you don't have to. Just know, and accept the trade off.