That way I have offsite storage in case the house burns down or something equally unlikely
That's what I thought. At first I had my PhD work in a single computer, which was obviously dangerous. As the data started growing I put it in a DVD. These days I have it in two computers and 1 dvd disc, all at home.
BUT what if the house collapses? 4 years of work wasted...
So, I also store it in the University server, and because they do backups every night I should be pretty safe...
BUT what if there's an attack on this little town where I live?! Like a bomb, or something to the same effect??
After all, I just live something like 60 miles from London, UK!
So, in addition I'm storing it in a server in Switzerland, which is quite a peaceful country...
Now, only if the whole continent burns down will I lose my work!

(in which case, I'm sure I'll have more to worry about than the bloody PhD...)