I have a 2 ton Bryant Heat Pump. It is usually 40-50 F at night outside. The room temp on thermostat measures 68. At night I set it to 69-70F . When I do this the air blowing out is not as warm as it should be(it is around 74-75F) and this makes my heater just run for a long time until it sets it to 70F. However, when i set the thermostat to like 74F I notice the thermostat says +1( i guess for aux heat) and air blowing out goes to like 87F. But then it will runs until it reaches around 70-71F and just puts out that cooler air (74F ) and just run for a long time. my thermostat is near the door and there arnt any vents near the themostat so takes forever to warm down if the air blowin is just 74F.

Whats the problem? does it cost more to where it just runs for long time vs. when thermostat decides to turn on aux heat at random?

Another problem, say the room temp is 69F, and I set the thermostat to 70F, theres only that warm cool(74-75F) air that comes out and it just runs a much longer time. how can i solve this? should i get new thermostat