If I haven't copied anything to or from my flash drive, I will usually just take it out anyways. Otherwise I will usually reboot my computer as that will also clear the flash drives cache. If the flash drive is not cleared, files copied/saved to the flash drive may become corrupted. For example, I spent several hour working on a powerpoint presentation and when I was done I saved, closed powerpoint and removed my flash drive without thinking. I was unable to open the powerpoint later so I had to startover.