OK, Labman and others proved very helpful in the past with my ignitor problem so now I have another question: How long should a proper furnace run between cycles?

I have read about the flame sensors and "limit switches" but I'm not sure if this is related to either. My heater seems to go off and on very frequently. For example, it has gone off and on about 6 times in the past hour and a half. Each time it runs for anywhere from 2 to 3 minutes but blows plenty of hot air. I have my thermostat set to 68 degrees at all times and the house seems to be maintaining the heat. At one point I set the desired temp to 72 degrees and it ran for 8 minutes before shutting itself off. The thermostat never went up in temperature so I assume it was keeping itself from overheating? So I'm not really sure if I should be complaining or even considering calling the same HVAC tech out (another service call? Sigh).

So now I'm wondering if this is how an efficient gas furnace should operate or if this is a sign that yet something else is out of sync. Another tidbit of info is every morning when I get up around 6 am the usage log tells me that it has been running for approximately 2 hours throughout the night.

My instincts tell me this is not normal (any maybe why my ignitor burned out so quickly last time) but maybe someone can tell me otherwise?