370z vlsd?
 

I know it's not the best diff by a long shot, but I think it will do the job on the street for me, and limited HPDE use.

However, I have heard that by 60K miles, the fluid inside the VLSD center unit is toast.

How have you guys found this to be? Is it still holding up, or do you have a 1-wheel wonder after a few HPDE's and 20-30K miles? Anyone with over 60K miles who can comment?

Does it stay its half-*** self, or does it indeed degrade with miles/track-time?

It does degrade if you track it, just like any diff. Also, the problem with viscous couplings is that as the differential oil temps increase, the ability to hold power between the two wheels is reduced which is why it isn't well suited for prolonged high performance driving.