I agree with DonM, if the stick is constantly jostled, banged up/down/sideways, I could see the port stop working. Other than that, as long as there is a sound electrical connection, there is no way it should stop working; UNLESS it is a very cheap USB stick that deteriorated over time. Some memory chips have been known to do that; especially with a high frequency of writes and erasures. Even the new SSD Flash memory drives do not have an infinite MTBF.