Still the same avg. speed?
(I'll give it a try on my F3 as well)
Media Wearout is either more correct on the SF or not working at all.
The 90% Wearout on One_Hertzs 320 would lead to about 180TB of Host Writes.
Still, with the MWI at 0 it can work for a long time, depending on whether there is sufficient spare-area left.