The answer to 'how long will installation last' is that a typical HVAC system installation will last between 8-12 hours for a standard residential system. The exact time can vary depending on the complexity of the system, the size of the home, and any existing ductwork or electrical work that needs to be done. Professional HVAC installers will generally be able to complete the full installation in a single day.
HVAC installations require specialized knowledge and tools, so it's best to have a licensed and experienced HVAC technician handle the job. They will ensure the system is installed properly and to code, which is important for both safety and efficiency.