I've been in a similar situation....
We had sizeable bonuses the past two years. We were already maxing out 401k plans and TIRA to Roth conversions, and saving some in After-tax accounts too...so what to do with the money?
We could simply "save" it, but we agreed in the end that paying down the mortgage was the right thing to do. We were at 5 3/8% at the time, on a 15-year fixed. We didn't have quite enough to pay "all" of it off, but we paid a big chunk, and then opened a no-fee HELOC at a different bank. The HELOC served two purposes.
1) Allowed us to pay off the remaining piece of the first mortgage, at a current rate of 3.5% (it is variable, but we are on a schedule to pay that portion off in less than 2 years)
2) Purchase rental properties
That was all done one year ago. Looking back, it was a good decision for us. We're now 1 year from REALLY paying off our primary residence via the HELOC. We also now have 2 rentals, one of which is fully paid for, the other which we owe about $30k on and plan to have paid off in about 3 years or so.
You will lose the tax deduction on paying off the house, but that's ok.
One tip for you, although my next statement is for Indiana...so your state may be different. If you pay off your mortgage completely, you may lose the mortgage exemption on your property taxes. For us, this would have cost us about $250/year. With the HELOC, we're able to maintain that deduction so long as we have a balance. Certainly I won't keep using the HELOC only
to get that exemption, but it's one more small factor to consider.
Edit: One other piece of advice. Make sure to keep liquidity somehow. IMO that means a 6-9 month of expenses emergency fund and a good anticipation of any large future expenses (remodel, car, new house, big vacation, more rentals