first of all some background.
Windows prevents you from ejecting a flash drive if its in use to prevent corruption of files that you are working on. Sometimes, programs don't release the flash drive back to the system. When this happens, windows won't allow you to safely eject the drive becuse it thinks the drive is still in use.
Does safely eject even matter?
Yes and no. If you are working on a document off your flash drive you MUST safely eject while the doc is open. You will get a message that the drive is in use. If you pull out the drive while a doc from it is open, you run the risk of corrupting that document.
If you aren't interacting with the flash drive (no pics, docs, vids, programs open ect.) then you can pull out the drive without doing the windows eject.