Will constantly running a central AC system on a... (by 3 users)

Nothing will be ruined, but you are wearing out the AC at a much higher rate than necessary. You may want to get it serviced once a year, to maintain proper efficiencies. Average lifespan of an AC unit is 12 -15 years, although no one uses them that long.

Central air conditioners is made up of an outdoor unit (the condensing unit) and an indoor unit, the air handler. The function of an air conditioner is to transport heat from one station to another. The vehicle your system uses to carry the heat is called a refrigerant, or Freon.
The compressor in your outdoor unit changes the Freon into a high temperature, high pressure gas. As that gas flows through the outdoor coil, it loses heat and condenses into a high temperature, high pressure liquid. This liquid refrigerant travels through copper tubing into the evaporator coil. There the refrigerant expands. Its sudden expansion turns the refrigerant into a low temperature, low pressure gas. This gas then absorbs heat from the air circulating in the duct work. The cooled air is then distributed back through your house or place of business. Meanwhile, the heat absorbed by the refrigerant is carried back outside through copper tubing and released into the outside air.
Dirty coils and improper refrigerant levels can cause your system to cool less efficiently than it should. An inefficient system means higher energy bills. It also forces your compressor to work harder than is necessary and can actually shorten the life span of your unit. An annual air conditioning inspection by an experienced technician includes an inspection of the coils and the checking of your refrigerant charge, to insure that your system is running efficiently.