Another thing that people often point to as a negative thing about ketosis is that people can suffer symptoms such as headaches and dizziness in the first few days of a ketogenic diet. Also, athletic performance can suffer until the body adapts to using fat for energy instead of glucose.
Forced air furnace heat exchangers have an average life expectancy of 15 years, with a range typically between 13 and 20 years. Most heat exchangers used in models today today will last between 15 and 25 years and are usually made from aluminized or stainless steel.
Oil Furnace Service Life. Many oil furnace manufacturers offer a 10-year warranty, but this doesnât always indicate the actual lifespan of the furnace. The average life expectancy for a properly maintained oil furnace is usually 15 to 20 years. Some furnaces may last as long as 25 years. The key to efficient operation of your oil furnace is annual maintenance by a certified HVAC technician.