Depends on how u use them!
Shocks/struts is a wear n tear item, the harder u push it to its limits, the sooner they'll need replacement.
Logically if u had them set to full stiff, I would safely guesstimate that the shocks will wear down sooner than someone who's had them on full soft. Also keep in mind that the more u lower the ride height the more stress is placed on the shocks as well as other suspension components as well.