I have had 2 external drives fail after I stupidly dropped them - admittedly onto the pavement on loading my car. If it is ok now you are probanly ok, but as these drives are reasonably priced. I would be inclined to back it up,- if your data is also on the main PC maybe no worries. Incidentally, and out of curiosity, why do you need such a massive drive?
Sony Xperia Z5 review: Hands-on with the phone which the Z3+ should have been