For the winter we keep our lowest thermostate heat setting on 55 and I want to change it to 50 but my husband says that he heard if any lower than 55 the pipes can freeze or burst. Is this true or simply an old wives tale? What would be the least temperature with the least amount of worry? We usually keep the temps down to 55 for sleeping in the winter... can the pipes tolerate lower temps all day and all night long?