I have 60K miles on my bilstein HD + Rallitek springs. I took my rears apart today cause the car feels bouncier than it should and I found that I can compress the struts (without springs of course) 'by hand'. As in, put the tip against the ground and push down on the opposite side. It doesn't take too much effort to do this but it does come back to full extension after a couple of seconds.
They seem weak to me but 60K shouldn't be end of life for them I wouldn't think.
I can't imagine they are providing much dampening at this point.
Problem is, I can't remember how they were when new. Has anyone tested theirs or have gone through enough mileage to call them used up?
BTW - I haven't seen any leaking or other indicators that they would be dead.