This depends on the amount of traffic over the turf and the type of turf selected by the customer.  Turf manufacturers have dramatically improved the resiliency of turf fibers so they have better “spring back”.  However, with enough traffic over the turf by either people, vehicles or service contactors, artificial turf will matt down eventually.  Choosing a turf product that isn’t too soft and has fibers shaped to resist matting helps significantly.  Not all turf types are equal in this regard.  Preventing matting can be improved with maintenance – powerbroom service and adding infill material.