External hard drives are great and really affordable too.  But, I hope you mean that you are "backing up" to an external hard drive.  Hard drives have been known to fail.  You always want to make sure that you have a second copy somewhere, just in case. 

I have had a couple of close calls over the years.  Our database crashed and I realized that I hadn't made a back-up in over a month.  Even a months worth of work is too much to lose.  We were fortunate enough to be able to get the database fixed with no loss of data.  After the second time of swearing to do regular back-ups, I finally automated it.  It backs-up nightly while I am sleeping... and I sleep much better knowing that.

Best,
Robert A. Franco
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