Hi Mike, Yes, I am concerned but not concerned enough to put up with the hassle and expense of making other arrangements. I am an amateur and do not rely on my photos for my living so the photos are less critical to me. Of course they are important to me. You are probably wise to consider putting your backup in another location. Obviously that is safer. Although I don't like the idea of entrusting that to a third party, it is, on balance, probably the safer thing to do. Putting backup drives in a safe deposit box is another possiblility for photos to which one does not need regular access.
I don't think you will have any problem managing the larger files produced by the D800.