Swifts killing my Nismo Struts?

[JJ-NISMO]

All,

I installed my Swifts 13 months ago, and until recently everything was smooth and fine. After about 12,000 miles on them, I have started to notice that if I am at high speed, such as highway driving, if I hit a bump or ridge, the shocks compress "harder" than they used to and I hear a sound like air being pushed out of them. Any thoughts?

My fear is that the struts are beginning to go. Swift ensured me that everything would be fine and that they designed the springs for the 370z, but I wonder if the increased stiffness is reducing the life of the stock struts significantly. If the struts are going, what can I do?

I have the Nismo. Swifts, with rear SPL camber kit. I live in Orange County in case it helps with road condition questions.

Thanks for any help.