Average Life Expectancies

Here are a few examples from historical data and experience:

Air conditioning compressor – air cooled, hermetically sealed
12 to 15 years
Air conditioning compressor – water-cooled, hermetically sealed
20 years
Air conditioning compressor – reciprocating 20 years
Rooftop heating and air conditioning unit 20 years
Copper core boiler – heat exchanger 15 to 20 years
Steel core boiler – heat exchanger 10 to 15 years
New cast iron core boiler – heat exchanger 20 to 25 years
Old cast iron core boiler – heat exchanger 30 to 50 years
Steel tube boiler – heat exchanger 20 to 40 years
Heat exchanger – standard rooftop unit 15 to 20 years
Heat exchanger downstream of a cooling coil (package unit) 10 to 20 years
Heat exchanger – standard  combustion indoor system 20 to 25 years
Cooling tower 20 to 25 years
Central chiller 20+ years
Air handler  30+ years
Gas-fired ceiling-mount unit heater 15 to 25 years
Gas-fired ceiling-mount radiant heater 20 to 25 years
Built-up asphalt and gravel roof system 20 to 25 years
Modified bitumen roof system 15 to 20 years
Inverted EPDM rubber or PVC roof system 25+ years
Asphalt paving for car parking 20 years
Asphalt paving for trucks 15 years
Sealed, double glazed windows 20 to 30 years
Plywood overhead doors 15 to 25 years
Pre-finished steel overhead doors 20+ years
Electrical transformer 30 years
Electrical switchgear 30 years