Flash Drive Lifespan
Flash drives do have limited lifepsan. Eventually they will wear out. Both primary components. the flash memory and the USB interface will break down over time.
The flash memory of a typical USB drive will allow for 5,000 writes. That means after a number of saves to the drive, it will stop functioning. The failure mechanism for flash memory cells is like metal fatigue. The USB drive simply refuses to write new data to individual cells that have experienced heavy use.
There is no practical limit to the number of times the data my be read. Some flash drives have a read only switch that you use to preserve it. Using such a switch will prevent further writes to to the drive.
The USB interface can also wear out. Manufacturers build the male adapter to function through 1,500 uses. This means that each drive should last for fifteen hundred plug in remove operations. Of course, the device may actually function beyond that, but you should not count on it.
I personally an never lost a flash drive to either failure. I have manage to smash them and misplace them. But none of mine have every failed to work.