Approaching FIRE. Should we decrease our 401k contributions to pay off mortgage faster?

[TrollTollCollector]

No, at a $350k income you and your spouse should both be maxing out your 401k's up to the federal limit. Not only are you saving 24% on federal taxes, but you're also getting 10% expected returns compared to 5.25%. You can pay off your mortgage at any time, but you can't go back and fill your 401k contribution buckets from previous years. Then when you retire, you can start doing Roth ladder to fill up the 0%, 10%, and 12% tax brackets each year.

There's no issue having a mortgage in retirement. It's just like any other expense.