I have a Rheem upflow gas furnace. When the furnace calls for heat, the electric ignitor lights up the gas. The flame is on for about 30 to 40 seconds, then the blower comes on. The flame is still on for another 15 to 20 seconds, it shuts off, however, the blower is still on. For another 30 to 45 seconds, the blower shuts off and this completes 1 cycle. Is this the correct process for a hot air gas furnace. I have the thermostat set at 60 degree. Should I set my thermostat at 65-70 degree if I want the flame to stay on longer after the blower comes on.