A suspension alignment should be performed on a regular basis to ensure proper tire to road traction, stable steering, and overall mechanical health and longevity of the suspension parts. The typical amount of time between alignments is three to six months; however, driving in rough conditions will shorten this period. Every time your vehicle crashes into a pothole, the suspension system is pounded with tremendous amounts of force. The weight of the vehicle combined with the speed and momentum cause considerable stress on suspension parts, every time you encounter a bump. Even if you do not drive off-road, most public roadways have deformations that put your suspension system through its paces.
For more info, see The Hidden Costs of Lowering Springs