In reading through the discussion in this thread, it is apparent that some folks do not understand that USB drives wear out with use, and the Pause/Replay function, as implemented in the ROKU TV is essentially a torture test for such devices.
First off, the USB thumb drive we all know and love was never intended, nor designed to operate as a continuous streaming device. Every time it is re-written, it is physically degraded. A cheap USB drive, which is what most of us buy, can be expected to support maybe 10,000 write/erase cycles. Some fall far short of that number. Some fall very, very, very short of that number. But, in the usage mode that most people employ them, this is not really a factor. If you are using one on a daily basis to carry documents around to and from the office, you might see a few 10's of cycles per week, if you are a real go-getter in the office.
However, in the ROKU Pause/Replay application, the USB drive is in the path of the antenna stream at all times you are watching OTA programming. Given that a 16GB drive is filled and dumped every 90 minutes, it is reasonable to estimate that the drive will see perhaps 6 - 10 cycles per day. So, given this set of conditions, it would be unreasonable to expect even a GOOD USB drive to last more than a couple of years in service.
BUT
The wear that occurs inside the USB drive is not necessarily uniform. The actual number of write/erase cycles in different places with the USB drive depends on several factors, including something called Wear Leveling, which is a process used within the USB drive to try to equalize the wear within the device, to prevent premature wear-out at a specific memory location, and bad-block replacement, in which memory locations which fail prematurely are swapped with a small stock of spares which are built in for such a purpose. Also, the internal book keeping of the USB drive itself has dedicated memory locations which are also written and erased at a rate which exceeds that of the general data storage.
THE BOTTOM LINE
From the above discussion, it is anticipatible that a USB drive will wear out in less than a year, given more than a couple of hours per day in service. In my own experience, I have seen wear-out related failures in the 9 month to 1 year span during the time this feature has been available and activated. It is also reasonable to understand that not all brands of USB drive are equal, either due to component quality or internal operating processes. Price is not necessarily a determining factor. I have found a specific low-cost USB drive which seems to do fairly well in this application, and that's the one I use (store brand at Office Depot). As with anything, Your mileage may vary.