Tell me a lot about the house, age of the house, type of construction, nearest city.. etc.
As a person approaches extremes, minor changes can have exponentially benificial effects.
A combination of changes such as mattress warmers and night set back to 55F can also save massively on your utility bill.
Doing the math on your carrier unit might show that we can run it down 10F outside with some benefit, the life cycle costs of that approach will be determined by the local climate... if it only rarely gets that cold then it would be a benefit.
Older systems for instance were designed to have no more than 10% air leakage from the ductwork, if that has not been rectified, and insulation is marginal, and window frames and doors leaking, those alone can double you required heating capacity. You can have a infra red camera study done on your house that will expose those heat leaks (often free by an insulation company.)
Let me know, we can go from there.
If those can be corrected then what you have in place might well be more than sufficient. Especially if have a large kitchen exhaust fan that runs a lot, and do not have an HRV (heat recovery ventilator).