H&R Spring

How is the handling wit these springs? Are there any concerns to fit some springs (-30mm in the front and -40mm in the back) on an original F1 suspension?
 
I used to own a twingo GT and lowered it on Eibach by what I can remember 30mm and after 6 month one of my dampers (stock one) was leaking. Any body else experienced that on their car or was it just bad luck ?