Proper long term use in the field data analysis by Graungroolz suggests that, like for platter drives, it's time in use not amount of use which is the lifetime limiting factor of flash drives. Something of the order of 5-6 years' heavy drive enclosure (i.e. data centre) use, perhaps longer, but certainly far less than the predicted life time which is predicated solely on running out of write cycles/wear levelling.
F'rinstance, if you hammered a 64GB flash drive continually at 80MB/s, you'd run out of write endurance after about 51 years. The drive will almost certainly fail before then, but not due to the re-write limitations, just auld age.
+1 for Samsung btw