I dispute the claim that the 2008 models were affected.
My px60u measured about 0.033 ftL
My px75u measured about 0.024 ftL
Both my px80u's measured about 0.016 ftL
They did not seem to change over the year I had each of them. (The 2008 px80u's were carefully measured with a meter over the 1500 hours of use that I had them.)
Both my X1s started out at about 0.014 ftL and now they both are at about 0.022 ftL. That's not three times. That's not even two times. These measurements were taken at about 200 hours and 4000 hours respectively. The instrument used was my i1 LT profiled with my certified i1 Pro.
Maybe next year I'll buy a couple of 2011 Panasonic models -- if they resolve the floating black issue. If not, maybe I'll try a different manufacturer. (My px75u had the floating blacks and I'll take the rising black level over that anytime.)