What temperature do you leave your home at

Today, I had my furnace guy come for the annual check-up, cleaning etc. I've known the guy for many years. I was telling him that next year we would be spending winter in the South and was planning on setting my furnace thermostat at 50 Degrees. He advised me not to do that. He said 60 Degrees minimum for my high efficiency furnace. He said moisture will accumulate in the heat exchanger if the furnace doesn't cycle enough and get hot enough. The life of the furnace will be reduced. I had never heard of that before. He said to think about it like a car exhaust. If all you do is drive it to the store and back, the exhaust never gets hot enough to evaporate the moisture and it rusts prematurely. He said the same thing happens with these high efficiency furnaces. So what do you think? What type of heating system do you have and what temperature do you leave your thermostat set to when away?