Various factors, only some within your control, can determine the life span of your air conditioning system.  Proper and regular maintenance will help your cooling system stay in premium running condition for years to come.  A well-maintained air conditioner may last up to 17 years!

"An air conditioner should last about 15 years. If a system that's more than a decade old begins to falter, consider total replacement of inside and outside units rather than a major repair. Usually only one of the system's major components--coil or compressor--fails, but it's usually more cost-effective to replace the whole system at once. Unmatched major components can compromise efficiency and lead to added repairs." -1999 Consumer's Reports Buying Guide, Central Cooling Systems, pg 143