The answer to 'lifespan of replacement' is that the typical lifespan of HVAC equipment can vary widely, but most systems have an average lifespan of 15-20 years with proper maintenance. The actual lifespan will depend on factors like the equipment quality, how well it was installed, and how well it's maintained through regular tune-ups and cleaning.
For example, a high-quality furnace or air conditioner that's well-maintained may last 18-20 years, while a lower-quality system or one that doesn't get regular service may only last 12-15 years. Proper installation and sizing of the equipment also plays a big role in how long it will last.