To answer one of your questions - Springs and struts usually have a 5-8 year life span depending on the load that they are carrying and on what types of roads you are driving on. Koni's and h&r have a LIFETIME Warranty (for as long as you own your car and you also have to have a Certified koni/h&r tech install them from you)
Well,
First off the koni struts(REAR) have 3 perches on them to set your springs on.
Meaning on the lowest perch they spring will sit about .25 inches lower than factory springs (meaning you should have a .25 drop with factory springs and koni struts)
The middle perch is suppost to be like stock hight, meaning with factory springs and the struts perch in middle you get the factory hight.
If you place the perch in the top position you will have a .25 raise from factory, so your car will look like the back is raise up a touch with factory springs.
So in theory if you place your springs on the highest koni perch your back will be up .25 inches and the back will be down .25 inches, but becareful as when the car is not level it can sometime be more bouncy than usual.
In my opinion, I suggest you change everything one time and never worry about it again.
Good Luck
Well,
First off the koni struts(REAR) have 3 perches on them to set your springs on.
Meaning on the lowest perch they spring will sit about .25 inches lower than factory springs (meaning you should have a .25 drop with factory springs and koni struts)
The middle perch is suppost to be like stock hight, meaning with factory springs and the struts perch in middle you get the factory hight.
If you place the perch in the top position you will have a .25 raise from factory, so your car will look like the back is raise up a touch with factory springs.
So in theory if you place your springs on the highest koni perch your back will be up .25 inches and the back will be down .25 inches, but becareful as when the car is not level it can sometime be more bouncy than usual.
In my opinion, I suggest you change everything one time and never worry about it again.
Good Luck