I finally threw together some graphs, see http://kegel.com/wine/yagmarkdata/wine-1.1.44-245.html Not sure what to make of the results yet.
Cheap thought, expansive solution:
Looking at the graphs and used HW i think this not necessary do what you expect. Change from 11 -> 10 can be just a normal deviation during measurement. But change from 100 -> 90 (80...) can show clearly performance regression.
Unfortunately latest nVidia cards have too high power consumption even in idle state (although internal logic underclock the GPU/RAM card heavily when idle). So running 24/7 brings another high cost :-/