How do i operate thermostat and furnace

Question

our furnace does not respond to the thermostat setting in a timley manner. At times it has taken approx. 24hr for the furnace to heat the home at the temperature set on the thermostat. I must admit that the thermostat settings have been increase irratically out of frustration that come from not being comfortable. Once the furnae and thermostat cooperate and the heat is adjusted in or home we are ok. We also hesitate to lower the temperatue setting below 70 on warmer days because we always have to struggle with the furnace and thermostat when it is time to increase the heat temperature for fear we may be cold for 24hr in temperatures below 40. Is our furnace faulty? It is failry new only1.5 years old. Or do we need to learn to operate it more efficiently? Last year the service repair man told us not to turn the heat below 70 in the winter time because the furnace will have to work to hard when it is time to turn it up again and that is why we were cold for 24hours last year. But shouldnt we be able chacng ethe setting on our thermostat and not worry about the furnace malfunctioning?