how much life do they increase your shock by? say i have the new koni str.t shocks with top hats lowered about 2.5", does that increase the life of the shock as if i only lowered the car 1.5"?

 

Not necessarily. Shock life depends upon spring height AND spring rate. If you use springs that are too stiff (which may be the case if they lower the car that much) then no amount of extended upper mount will help the shocks. They might last a LITTLE longer but probably not much. The stiff spring rate will still over-work the shock beyond what it was designed for.