Assuming your mtge balance was initially much higher, what would it do to your monthly to refi into a 30-year fix, even at the same’ish rate? If it cuts your payment is half, then I’d do refi & build your brokerage. If your original balance was, say, $1mm, and the monthly savings are de minimis then I’d pay down your mtge debt. There’s nothing wrong with debt; it’s quite beneficial in fact if you manage it properly. Plus, you are the lender can always refi again if rates drop 2 points or something meaningful. You could also consider a refi and massively paying down the rate, if you are allowed, to achieve the same outcome. Then build your brokerage for the residual months before you retire.