Hi, just wondering... Are external hard disks designed to be turned on 24/7? I think I fried one of my 500 Gig external hard disk because I turned it on for way too long? Is it possible?

What happens now is that while it still can still be recognised by my MacBook, whatever content that I write into it won't be retained the next time I boot up and I constantly have to re-format the hard disk anyway because it frequently gets screwed up (especially after I put stuff into it).

I know what I had described isn't exactly very "technical" or specific... But any help on this matter will be greatly appreciated.