Installation in an average home will only cost around $200. If you are already paying $1,500 to $4,000 for a system, it's a small price to pay for peace of mind. The average ductless mini split air conditioner, with proper care and maintenance, will have a lifespan of 12 to 15 years.If you live in an area with high humidity or salt, your system may not last quite as long. The best maintenance you can provide your system is cleaning it. Clean and change your filters.nstallation in an average home will only cost around $200. If you are already paying $1,500 to $4,000 for a system, it's a small price to pay for peace of mind. The average ductless mini split air conditioner, with proper care and maintenance, will have a lifespan of 12 to 15 years.