When a wheel reacts to a bump or body motion, the shock or strut is cycled. In this cycle, the piston will move and the valves inside the unit will pass fluid from one side of the unit to the other. It’s not the length of the stroke that matters, but the frequency of the cycles. Even under normal conditions on a smooth road, shocks can cycle an average of 1,750 times for every mile traveled. This can add up to almost 9 million cycles in 50,000 miles.