The lifespan of a building hoist is determined by several factors including its design, materials, usage, maintenance, and compliance with safety standards. Regular inspections and maintenance are crucial to assess the hoist's condition. A hoist should be replaced when it shows significant wear, has been in service beyond the manufacturer's recommended lifespan, or fails to meet safety standards. Additionally, any hoist that has been involved in an accident or has undergone major repairs may need to be replaced to ensure safety. Consulting the manufacturer's guidelines and local regulations can provide specific information on when a hoist should be retired.