Offhand, that sounds like a counterfeit flash drive. However, the few counterfeits that I've purchased (usually on eBay) usually had something really gross wrong with them, such as claiming to be a 64GB drive, when it would hold only 2GB. Still, it's possible that there's a quality issue with whatever you're using.
That sounds like spare blocks being depleted.
Reading from flash is never a problem. It's writing that eventually kills them. In order to write one lousy byte, the controller on the USB drive needs to read an entire block (size varies with device), erase the block, change one byte in the block, and write the entire block. That's why reading flash is quite fast, but writing is much slower. In other words, don't worry about reading.
That's another way to kill flash drives. See: 5.1 Erase before Write Sandisk erases one block at a time (4MBytes) and writes one page (16KBytes) at a time. So, if your data logger slooooowly writes one byte of data every few seconds, the flash drive will need to erase
4MBytes every second, and write 16KBytes every second. Even if succeeding writes are to sequential bytes, it will still require 16,000 erases and writes to completely write 16KBytes of data at 1 byte per second.Well, actually it's not that awful. If the writes arrive quickly, the flash controller will buffer the writes, and wait for a convenient time to flush the buffer in one big write. The idea is not to buffer the data for too long before flushing. That's why I specified one byte per second. That's much slower than the normal buffer flush timeout.
Incidentally, if all you want is something that doesn't stick out too far, think about a right angle USB adapter like these: Something like this: which seems somewhat low profile. Of the 90 degree flavor, there are
4 different orientations, so be careful when ordering. I have one of these on a laptop where I use the USB drive for a data drive (so that no live data remains on the laptop in case it's stolen). The right angle adapter isn't perfect, but at least it fits in the laptop bag without (much) snagging.