Can a Trane furnace last 40 years?

Can a Trane furnace last 40 years is possible for very old heavy-duty models but extremely rare and not expected for modern furnaces, as average life of Trane furnace is 18 to 22 years and maximum with excellent care is 25 to 30 years. Old Trane furnaces from 1970s and 1980s built with very heavy cast iron heat exchangers and simple controls could last 30 to 40 years if heat exchanger did not crack and parts like gas valve replaced, and some still operating today at 35 years. Modern Trane furnaces from 1990s onward use thinner aluminized steel heat exchangers, more electronics, and variable speed motors that typically fail after 15 to 22 years, with heat exchangers developing cracks after 20 years due to thermal stress, and control boards failing after 12 to 15 years. Factors that could allow Trane furnace to reach 40 years include running only 3 to 4 months per year in mild climate, annual maintenance, low usage, and replacing major parts like blower motor twice at 400 to 700 dollars each, gas valve, and igniter multiple times. However, after 20 years, furnace efficiency at 80 percent AFUE versus modern 96 percent causes higher gas bills, and parts become obsolete, and safety risk from cracked heat exchanger that can leak carbon monoxide increases significantly after 20 years. Most HVAC pros recommend replacing after 20 years for safety and efficiency, even if still operating, so while 40 years is technically possible for old unit, it is not practical or safe for modern Trane furnace.