When to replace the shocks?
But I am not after that answer... (and you will probably give it anyway 
Shocks don't appear in the maintenance booklet. Why? How to know when they need replacement?
How about the springs? When do they need replacement?
Thank you,
Ali
If you are happy with the stock shocks' ride/handling quality, then you only need to worry about them wearing out.
you can test them by compressing the suspension: pushing down on the fender, (hood open may help) getting it in to a slight up and down rocking motion, then release. The strut should return to it's resting position. If it noticeably continues to move, it's toast.
They aren't in the service manual because the life of a shock is obviously going to depend significantly upon how and where it is driven.
Springs can be a lifetime item. They shouldn't sag. Never kept a car (or the OEM springs in them) for long enough to get them to sag. My GTI has 155K on stock springs, and that is nothing remarkable.




