I defrag my computers once a week and have been doing so for over 10 years with all the various computers I've owned. I don't feel defragging would cause premature HDD failure because most times when I do defrag it only takes a few minutes and I feel that's nothing to be concerned with. I do feel a little anxious when I do run defrag on a computer that hasn't been defragged in months (or even years) and the defrag takes a really long time but I don't think I've ever seen a computer die during or right after a defrag has been performed.
When I build a computer for someone I write down some instructions on how to perform simple computer maintenance on their new computer (manual virus and malware scans, disk cleanup, defrag, etc...) and how often it should be done. It's up to the new owner if he wants to follow those instructions or not. They paid for the computer and it's their responsibility now, not mine.
The way I look at it is this...it's your computer and you should be able to do whatever it is that you want to do to it. If you don't want to run defrag on the hard drive, then don't. If you do want to run defrag on your computer, then go ahead and run it. It's
your computer, not anybody else's.
Cricket