When I import files into the database, should I delete the original files?

That’s up to you. I either delete import-captured files or archive them onto another storage device.

In any case, make sure that you have a good backup strategy for your important files. Bad Things such as a hard drive crash or lost or stolen equipment can and do happen. For users of DT Pro or DT Pro Office I recommend File > Export > Database Archive, which produces the smallest possible compressed and dated complete archive of a database. This archive can be saved on an external drive. There are similar backup procedures that provide for remote online storage in Scripts > Export — allowing one to send the database archive to iDisk or JungleDisk for storage.