A ballscrew actuator reaches its life after some time even when operating normally.
The life of a ballscrew actuator is the time until "flaking" starts occurring due to fatigue by repeated stress on the ball rolling surface of the ball screw, slide guide and bearing, and is defined as the shortest time or distance until "flaking" starts occurring.

Ball screws can only receive axial load. Therefore, it is the slide guide that receives the other loads, such as vertical load, moment load, etc. For this reason, the life of the slide guide is typically shorter than those of the ball screws and bearings, which receive only axial load.

The criteria of load that can be applied to an actuator are rated basic dynamic load, rated basic static load, and allowable static moment. Naturally, the smaller load results in the longer life and vice-versa.
However, choosing an actuator with larger size than needed just to obtain longer life will not only make larger the external dimensions larger, but it will also cost more, so you must choose an actuator of appropriate size that satisfies the desired life.

For more information on life due to "flaking", also see "How is Ball Screw Life calculated?" from Technical Information/Ball Screws.