I think what Sydneykid ment by skylines having coilovers from factory is, if you have a look at your stock suspension, the coil spring sits on top of the damper ("shock absorber"), hence the term coilovers. Coilovers is generally used as a name for a set of aftermarket suspension. They can have height adjustable capabilities etc etc
If you wanna lower your car, three options: get a set of lowered springs (and shocks to match), aftermarket coilovers (with base height adjustability preferably), or cut your springs (illegal).
I think the kings should last a couple of years if you have good shocks (some KYBs perhaps?) to support them, and generally don't do heavy cornering or off roading (). The weight of your wheels is also a factor
My 2 pence