No, but it does not mean it is a death sentence if you do.
You can not guarantee that all the writes have been flushed out, but after several minutes of sitting it is likely that the data is flushed out. However, you may have some issues with some filesystem maintenance things that don't happen until you unmount if you are in "Performance mode" (see the next paragraph)
However there is another option (and it is likely already set for 99% of all removable media). If right click on the device and go to properties. Then from there go to the hardware tab and find your device.
Properties, then click on the
Change Settings button on the new page. Go to the
If you device is set to "Quick Removal" you can remove your device without going though "Safely Remove Hardware" without worrying about data loss.
If you do not have a
Policies tab you likely skipped the
Change Settings step.